A question about how to read a csv file and output it

Hi!
My environment are centos6.7, python3.7, and pymars0.9.0. When I run the demo you give in zhihu [https://www.zhihu.com/question/320961999](url) , something seems to be wrong.
Here are my codes. I think maybe 'execute()' leads to the problem.

```
import mars.dataframe as md

df = md.read_csv('bin_end.csv')

df.execute()
```

Here are the error logs.

```
/usr/local/lib/python3.7/site-packages/mars/deploy/oscar/session.py:2064: UserWarning:
No session found, local session will be created in background, it may take a while before execution. If you want to new a local session by yourself, run code below:

import mars

mars.new_session()

warnings.warn(warning_msg)
Traceback (most recent call last):
File "my.py", line 5, in
df.execute()
File "/usr/local/lib/python3.7/site-packages/mars/core/entity/tileables.py", line 462, in execute
result = self.data.execute(session=session, **kw)
File "/usr/local/lib/python3.7/site-packages/mars/core/entity/executable.py", line 144, in execute
return execute(self, session=session, **kw)
File "/usr/local/lib/python3.7/site-packages/mars/deploy/oscar/session.py", line 1888, in execute
session = get_default_or_create(**(new_session_kwargs or dict()))
File "/usr/local/lib/python3.7/site-packages/mars/deploy/oscar/session.py", line 2065, in get_default_or_create
session = new_session("127.0.0.1", init_local=True, **kwargs)
File "/usr/local/lib/python3.7/site-packages/mars/deploy/oscar/session.py", line 2040, in new_session
address, session_id=session_id, backend=backend, new=new, **kwargs
File "/usr/local/lib/python3.7/site-packages/mars/deploy/oscar/session.py", line 1636, in init
isolated_session = fut.result()
File "/usr/local/lib/python3.7/concurrent/futures/_base.py", line 432, in result
return self.__get_result()
File "/usr/local/lib/python3.7/concurrent/futures/_base.py", line 384, in __get_result
raise self._exception
File "/usr/local/lib/python3.7/site-packages/mars/deploy/oscar/session.py", line 848, in init
address, timeout=timeout, backend=backend, **kwargs
File "/usr/local/lib/python3.7/site-packages/mars/deploy/oscar/local.py", line 91, in new_cluster_in_isolation
await cluster.start()
File "/usr/local/lib/python3.7/site-packages/mars/deploy/oscar/local.py", line 219, in start
await self._start_service()
File "/usr/local/lib/python3.7/site-packages/mars/deploy/oscar/local.py", line 274, in _start_service
config=self._config,
File "/usr/local/lib/python3.7/site-packages/mars/deploy/oscar/service.py", line 84, in start_worker
NodeRole.WORKER, config, address=address, mark_ready=mark_ready
File "/usr/local/lib/python3.7/site-packages/mars/services/core.py", line 174, in start_services
await asyncio.gather(*[inst.start() for inst in instances])
File "/usr/local/lib/python3.7/site-packages/mars/services/cluster/worker/service.py", line 68, in start
address=address,
File "/usr/local/lib/python3.7/site-packages/mars/oscar/api.py", line 27, in create_actor
return await ctx.create_actor(actor_cls, *args, uid=uid, address=address, **kwargs)
File "/usr/local/lib/python3.7/site-packages/mars/oscar/backends/context.py", line 112, in create_actor
return self._process_result_message(result)
File "/usr/local/lib/python3.7/site-packages/mars/oscar/backends/context.py", line 76, in _process_result_message
raise message.as_instanceof_cause()
File "/usr/local/lib/python3.7/site-packages/mars/oscar/backends/pool.py", line 525, in create_actor
await self._run_coro(message.message_id, actor.__post_create__())
File "/usr/local/lib/python3.7/site-packages/mars/oscar/backends/pool.py", line 343, in _run_coro
return await coro
File "/usr/local/lib/python3.7/site-packages/mars/services/cluster/procinfo.py", line 41, in __post_create__
allocate_strategy=ProcessIndex(index),
File "/usr/local/lib/python3.7/site-packages/mars/oscar/api.py", line 27, in create_actor
return await ctx.create_actor(actor_cls, *args, uid=uid, address=address, **kwargs)
File "/usr/local/lib/python3.7/site-packages/mars/oscar/backends/context.py", line 112, in create_actor
return self._process_result_message(result)
File "/usr/local/lib/python3.7/site-packages/mars/oscar/backends/context.py", line 76, in _process_result_message
raise message.as_instanceof_cause()
File "/usr/local/lib/python3.7/site-packages/mars/oscar/backends/pool.py", line 939, in create_actor
result = await self.call(address, new_create_actor_message)
File "/usr/local/lib/python3.7/site-packages/mars/oscar/backends/pool.py", line 402, in call
return await self._caller.call(self._router, dest_address, message)
File "/usr/local/lib/python3.7/site-packages/mars/oscar/backends/core.py", line 95, in call
await client.send(message)
File "/usr/local/lib/python3.7/site-packages/mars/oscar/backends/communication/base.py", line 258, in send
return await self.channel.send(message)
File "/usr/local/lib/python3.7/site-packages/mars/oscar/backends/communication/socket.py", line 73, in send
buffers = await serializer.run()
File "/usr/local/lib/python3.7/site-packages/mars/serialization/aio.py", line 85, in run
return await self._get_buffers()
File "/usr/local/lib/python3.7/site-packages/mars/serialization/aio.py", line 41, in _get_buffers
self._obj, spawn_threshold=DEFAULT_SPAWN_THRESHOLD
File "mars/serialization/core.pyx", line 766, in serialize_with_spawn
File "mars/serialization/core.pyx", line 660, in mars.serialization.core._serialize_with_stack
File "mars/serialization/core.pyx", line 598, in mars.serialization.core._serial_single
File "mars/serialization/core.pyx", line 258, in mars.serialization.core.PickleSerializer.serial
File "mars/serialization/core.pyx", line 223, in mars.serialization.core.pickle_buffers
File "/usr/local/lib/python3.7/site-packages/cloudpickle/cloudpickle_fast.py", line 73, in dumps
cp.dump(obj)
File "/usr/local/lib/python3.7/site-packages/cloudpickle/cloudpickle_fast.py", line 640, in dump
raise pickle.PicklingError(msg) from e
pickle5.pickle.PicklingError: [address=127.0.0.1:33346, pid=30517] Could not pickle object as excessively deep recursion required.
```

Reproduce the provided read_csv and execute() example in the stated Python, CentOS, and Mars environment, then start with the traceback entries in deploy/oscar/session.py, deploy/oscar/local.py, and serialization/core.pyx. Done means the example executes without the reported excessively deep recursion PicklingError and produces the requested CSV output.

Written by the indexing model from the issue text.