使用下标查询时，会出现很多次空查询

**(重要！问题分类)**
* 控件识别、树状结构、poco库报错 -> 此仓库

**描述问题bug**
使用下标查询元素时，假设此时child.__len__() = 19 ，那么会产生19次空查询 + 1次正确的查询，总共20次查询

**复现步骤**
脚本内容：

import time
from poco.drivers.std import StdPoco

begtime = time.time()
print(poco("Layout").child("cheatView").offspring("Top_Size_ScrollView_cheat").child("Node_single_input").__len__())
a = poco("Layout").child("cheatView").offspring("Top_Size_ScrollView_cheat").child("Node_single_input")[0].child("TextField_text").exists()
print(a)
print('耗时{}'.format(time.time() - begtime))

**预期效果**
使用下标时正常应该dump一次即可，目前会dump20次

**相关截图**
无

**python 版本:** `python3.6.6`

**poco 版本:** `1.0.79`

**设备:**
- 型号: [e.g. google pixel 2]
- 系统: [e.g. Android 8.1]
- (别的信息)

**其他相关环境信息**
运行日志输出：
D:\Python36\python.exe E:/debug_poco/ccc.air/ccc.py
E:\debug_poco\lib\airtest\core\android\static\adb\windows\adb.exe devices
E:\debug_poco\lib\airtest\core\android\static\adb\windows\adb.exe devices
E:\debug_poco\lib\airtest\core\android\static\adb\windows\adb.exe -s 03157df3ab476e26 wait-for-device
E:\debug_poco\lib\airtest\core\android\static\adb\windows\adb.exe -s 03157df3ab476e26 shell getprop ro.build.version.sdk
E:\debug_poco\lib\airtest\core\android\static\adb\windows\adb.exe -s 03157df3ab476e26 forward --no-rebind tcp:19498 tcp:15004
address is ('127.0.0.1', 19498)
[rpc]connected
运行原始build_query方法
Layout {}
and (('attr=', ('name', 'Layout')),)
运行原始build_query方法
cheatView {}
and (('attr=', ('name', 'cheatView')),)
运行原始build_query方法
None {}
and ()
运行原始build_query方法
Top_Size_ScrollView_cheat {}
and (('attr=', ('name', 'Top_Size_ScrollView_cheat')),)
运行原始build_query方法
None {}
and ()
运行原始build_query方法
Node_single_input {}
and (('attr=', ('name', 'Node_single_input')),)
运行原始build_query方法
None {}
and ()
send msg is b'd\x00\x00\x00{"method": "Dump", "params": [true], "jsonrpc": "2.0", "id": "326701a0-4bb9-4e56-9a2e-4a66678ba7c9"}'
msg len is 77087
sync_wrapper cb.wait 耗时0.18952393531799316
FrozenUIDumper.getRoot 耗时0.18952393531799316
getRoot 耗时0.18952393531799316
selectImpl 耗时0.0010001659393310547
selectImpl 耗时0.0
selectImpl 耗时0.0010001659393310547
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0
selectImpl 耗时0.0015001296997070312
19
运行原始build_query方法
Layout {}
and (('attr=', ('name', 'Layout')),)
运行原始build_query方法
cheatView {}
and (('attr=', ('name', 'cheatView')),)
运行原始build_query方法
None {}
and ()
运行原始build_query方法
Top_Size_ScrollView_cheat {}
and (('attr=', ('name', 'Top_Size_ScrollView_cheat')),)
运行原始build_query方法
None {}
and ()
运行原始build_query方法
Node_single_input {}
and (('attr=', ('name', 'Node_single_input')),)
运行原始build_query方法
None {}
and ()
send msg is b'd\x00\x00\x00{"method": "Dump", "params": [true], "jsonrpc": "2.0", "id": "988ebe20-7689-4710-8a64-cdc9b842579c"}'
msg len is 77087
sync_wrapper cb.wait 耗时0.22452855110168457
FrozenUIDumper.getRoot 耗时0.22452855110168457
getRoot 耗时0.22502851486206055
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0005002021789550781
selectImpl 耗时0.0010001659393310547
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0015001296997070312
运行原始build_query方法
None {}
and ()
send msg is b'd\x00\x00\x00{"method": "Dump", "params": [true], "jsonrpc": "2.0", "id": "aa8c7d85-0d35-480c-9568-d6c397335289"}'
msg len is 77087
sync_wrapper cb.wait 耗时0.18102335929870605
FrozenUIDumper.getRoot 耗时0.18102335929870605
getRoot 耗时0.18152332305908203
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0005002021789550781
selectImpl 耗时0.0010001659393310547
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0015001296997070312
运行原始build_query方法
None {}
and ()
send msg is b'd\x00\x00\x00{"method": "Dump", "params": [true], "jsonrpc": "2.0", "id": "0ac24566-0fc7-408c-a485-f5e7786e0fa8"}'
msg len is 77087
sync_wrapper cb.wait 耗时0.20002532005310059
FrozenUIDumper.getRoot 耗时0.20002532005310059
getRoot 耗时0.20052552223205566
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0009999275207519531
selectImpl 耗时0.0005002021789550781
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0015001296997070312
运行原始build_query方法
None {}
and ()
send msg is b'd\x00\x00\x00{"method": "Dump", "params": [true], "jsonrpc": "2.0", "id": "6b17bedf-fc94-4eb6-9dbe-bc40b7103db7"}'
msg len is 77087
sync_wrapper cb.wait 耗时0.2020256519317627
FrozenUIDumper.getRoot 耗时0.2020256519317627
getRoot 耗时0.2020256519317627
selectImpl 耗时0.0010001659393310547
selectImpl 耗时0.0
selectImpl 耗时0.0010001659393310547
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0015001296997070312
运行原始build_query方法
None {}
and ()
send msg is b'd\x00\x00\x00{"method": "Dump", "params": [true], "jsonrpc": "2.0", "id": "eeaa0a16-8675-45d5-b038-f6b47ddf40be"}'
msg len is 77087
sync_wrapper cb.wait 耗时0.2170274257659912
FrozenUIDumper.getRoot 耗时0.2170274257659912
getRoot 耗时0.2170274257659912
selectImpl 耗时0.0010001659393310547
selectImpl 耗时0.0
selectImpl 耗时0.0010001659393310547
selectImpl 耗时0.0005004405975341797
selectImpl 耗时0.0015006065368652344
selectImpl 耗时0.0
selectImpl 耗时0.0015006065368652344
selectImpl 耗时0.0015006065368652344
运行原始build_query方法
None {}
and ()
send msg is b'd\x00\x00\x00{"method": "Dump", "params": [true], "jsonrpc": "2.0", "id": "1d60cf35-8a81-41f8-9539-7059d9ce7bb0"}'
msg len is 77087
sync_wrapper cb.wait 耗时0.19902515411376953
FrozenUIDumper.getRoot 耗时0.19902515411376953
getRoot 耗时0.1995251178741455
selectImpl 耗时0.0005002021789550781
selectImpl 耗时0.0
selectImpl 耗时0.0005002021789550781
selectImpl 耗时0.0009999275207519531
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0015001296997070312
运行原始build_query方法
None {}
and ()
send msg is b'd\x00\x00\x00{"method": "Dump", "params": [true], "jsonrpc": "2.0", "id": "507c7ce3-796e-4ee0-99ec-438db4b11830"}'
msg len is 77087
sync_wrapper cb.wait 耗时0.21452713012695312
FrozenUIDumper.getRoot 耗时0.21452713012695312
getRoot 耗时0.2150273323059082
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0009999275207519531
selectImpl 耗时0.0005002021789550781
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0015001296997070312
运行原始build_query方法
None {}
and ()
send msg is b'd\x00\x00\x00{"method": "Dump", "params": [true], "jsonrpc": "2.0", "id": "b4cd5265-f462-48cd-913c-5f319a5cf447"}'
msg len is 77087
sync_wrapper cb.wait 耗时0.16402077674865723
FrozenUIDumper.getRoot 耗时0.16402077674865723
getRoot 耗时0.1645209789276123
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0009999275207519531
selectImpl 耗时0.0005002021789550781
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0015001296997070312
运行原始build_query方法
None {}
and ()
send msg is b'd\x00\x00\x00{"method": "Dump", "params": [true], "jsonrpc": "2.0", "id": "0e2b779d-c433-4370-a508-c9472ee455aa"}'
msg len is 77087
sync_wrapper cb.wait 耗时0.1600203514099121
FrozenUIDumper.getRoot 耗时0.1600203514099121
getRoot 耗时0.1605205535888672
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0009999275207519531
selectImpl 耗时0.0014998912811279297
selectImpl 耗时0.0
selectImpl 耗时0.0014998912811279297
selectImpl 耗时0.0014998912811279297
运行原始build_query方法
None {}
and ()
send msg is b'd\x00\x00\x00{"method": "Dump", "params": [true], "jsonrpc": "2.0", "id": "17b7c1a6-97c3-43c8-997b-2a2911ba0114"}'
msg len is 77087
sync_wrapper cb.wait 耗时0.21202707290649414
FrozenUIDumper.getRoot 耗时0.21202707290649414
getRoot 耗时0.21252703666687012
selectImpl 耗时0.0005002021789550781
selectImpl 耗时0.0
selectImpl 耗时0.0005002021789550781
selectImpl 耗时0.0009999275207519531
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0015001296997070312
运行原始build_query方法
None {}
and ()
send msg is b'd\x00\x00\x00{"method": "Dump", "params": [true], "jsonrpc": "2.0", "id": "8fc845d3-5d81-4d13-a1f5-937474aa6770"}'
msg len is 77087
sync_wrapper cb.wait 耗时0.1955249309539795
FrozenUIDumper.getRoot 耗时0.1955249309539795
getRoot 耗时0.1955249309539795
selectImpl 耗时0.0005002021789550781
selectImpl 耗时0.0
selectImpl 耗时0.0010001659393310547
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0015001296997070312
运行原始build_query方法
None {}
and ()
send msg is b'd\x00\x00\x00{"method": "Dump", "params": [true], "jsonrpc": "2.0", "id": "80dc46c9-5d7c-41f6-8bba-677bc9fe6664"}'
msg len is 77087
sync_wrapper cb.wait 耗时0.20752644538879395
FrozenUIDumper.getRoot 耗时0.20752644538879395
getRoot 耗时0.20802664756774902
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0009999275207519531
selectImpl 耗时0.0014998912811279297
selectImpl 耗时0.0
selectImpl 耗时0.0014998912811279297
selectImpl 耗时0.0014998912811279297
运行原始build_query方法
None {}
and ()
send msg is b'd\x00\x00\x00{"method": "Dump", "params": [true], "jsonrpc": "2.0", "id": "85e82b89-f382-4705-8470-dec1bdbc9e3f"}'
msg len is 77087
sync_wrapper cb.wait 耗时0.27953577041625977
FrozenUIDumper.getRoot 耗时0.27953577041625977
getRoot 耗时0.28003597259521484
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0009999275207519531
selectImpl 耗时0.0
selectImpl 耗时0.0009999275207519531
selectImpl 耗时0.0015001296997070312
运行原始build_query方法
None {}
and ()
send msg is b'd\x00\x00\x00{"method": "Dump", "params": [true], "jsonrpc": "2.0", "id": "0311671a-2523-45bb-ad2f-b50d2a08523c"}'
msg len is 77087
sync_wrapper cb.wait 耗时0.3910496234893799
FrozenUIDumper.getRoot 耗时0.3910496234893799
getRoot 耗时0.3910496234893799
selectImpl 耗时0.0009999275207519531
selectImpl 耗时0.0
selectImpl 耗时0.0009999275207519531
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0014998912811279297
selectImpl 耗时0.0
selectImpl 耗时0.0014998912811279297
selectImpl 耗时0.0014998912811279297
运行原始build_query方法
None {}
and ()
send msg is b'd\x00\x00\x00{"method": "Dump", "params": [true], "jsonrpc": "2.0", "id": "ecee0f6f-dab1-440d-a724-7c3343c338b5"}'
msg len is 77087
sync_wrapper cb.wait 耗时0.2150275707244873
FrozenUIDumper.getRoot 耗时0.2150275707244873
getRoot 耗时0.2150275707244873
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0
selectImpl 耗时0.0010001659393310547
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0015001296997070312
运行原始build_query方法
None {}
and ()
send msg is b'd\x00\x00\x00{"method": "Dump", "params": [true], "jsonrpc": "2.0", "id": "b6baf050-6f1a-4b34-9539-33220ad6ddcd"}'
msg len is 77087
sync_wrapper cb.wait 耗时0.20302557945251465
FrozenUIDumper.getRoot 耗时0.20302557945251465
getRoot 耗时0.20352578163146973
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0005002021789550781
selectImpl 耗时0.0010001659393310547
selectImpl 耗时0.0
selectImpl 耗时0.0015003681182861328
selectImpl 耗时0.0015003681182861328
运行原始build_query方法
None {}
and ()
send msg is b'd\x00\x00\x00{"method": "Dump", "params": [true], "jsonrpc": "2.0", "id": "87234bf8-1c92-4550-9943-41af2a2732e4"}'
msg len is 77087
sync_wrapper cb.wait 耗时0.19652462005615234
FrozenUIDumper.getRoot 耗时0.19652462005615234
getRoot 耗时0.19702482223510742
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0005002021789550781
selectImpl 耗时0.0010001659393310547
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0015001296997070312
运行原始build_query方法
None {}
and ()
send msg is b'd\x00\x00\x00{"method": "Dump", "params": [true], "jsonrpc": "2.0", "id": "6eb79008-877b-4538-a476-eb99f75deaf5"}'
msg len is 77087
sync_wrapper cb.wait 耗时0.2150275707244873
FrozenUIDumper.getRoot 耗时0.21552753448486328
getRoot 耗时0.21552753448486328
selectImpl 耗时0.0010001659393310547
selectImpl 耗时0.0
selectImpl 耗时0.0010001659393310547
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0
selectImpl 耗时0.002000093460083008
selectImpl 耗时0.002000093460083008
运行原始build_query方法
None {}
and ()
send msg is b'd\x00\x00\x00{"method": "Dump", "params": [true], "jsonrpc": "2.0", "id": "0d3d9302-5dae-4135-9547-bd388f4fffbc"}'
msg len is 77087
sync_wrapper cb.wait 耗时0.1755223274230957
FrozenUIDumper.getRoot 耗时0.1755223274230957
getRoot 耗时0.1755223274230957
selectImpl 耗时0.0010001659393310547
selectImpl 耗时0.0
selectImpl 耗时0.0010001659393310547
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0015001296997070312
运行原始build_query方法
None {}
and ()
send msg is b'd\x00\x00\x00{"method": "Dump", "params": [true], "jsonrpc": "2.0", "id": "4425db73-560b-413d-87ee-f66e4bc1b2fd"}'
msg len is 77087
sync_wrapper cb.wait 耗时0.21452736854553223
FrozenUIDumper.getRoot 耗时0.21452736854553223
getRoot 耗时0.21452736854553223
selectImpl 耗时0.0009999275207519531
selectImpl 耗时0.0
selectImpl 耗时0.0009999275207519531
selectImpl 耗时0.0005002021789550781
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0015001296997070312
运行原始build_query方法
TextField_text {}
and (('attr=', ('name', 'TextField_text')),)
运行原始build_query方法
None {}
and ()
send msg is b'd\x00\x00\x00{"method": "Dump", "params": [true], "jsonrpc": "2.0", "id": "ea3dc3e3-48c4-40e3-8234-7ae875813216"}'
msg len is 77087
sync_wrapper cb.wait 耗时0.16852140426635742
FrozenUIDumper.getRoot 耗时0.16852140426635742
getRoot 耗时0.1690213680267334
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0
selectImpl 耗时0.0004999637603759766
selectImpl 耗时0.0005002021789550781
selectImpl 耗时0.0010001659393310547
selectImpl 耗时0.0
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0015001296997070312
selectImpl 耗时0.0
selectImpl 耗时0.0015001296997070312
True
耗时4.667592525482178
E:\debug_poco\lib\airtest\core\android\static\adb\windows\adb.exe -s 03157df3ab476e26 forward --remove tcp:19498

进程已结束,退出代码0