ImportError: cannot import name 'anchor_generator_pb2'. Protobuf doesn't work here.

when I run this on google colab
!python object_detection/builders/model_builder_test.py

I get:
Traceback (most recent call last):
File "object_detection/builders/model_builder_test.py", line 23, in
from object_detection.builders import model_builder
File "/usr/local/lib/python3.6/dist-packages/object_detection-0.1-py3.6.egg/object_detection/builders/model_builder.py", line 20, in
from object_detection.builders import anchor_generator_builder
File "/usr/local/lib/python3.6/dist-packages/object_detection-0.1-py3.6.egg/object_detection/builders/anchor_generator_builder.py", line 22, in
from object_detection.protos import anchor_generator_pb2
ImportError: cannot import name 'anchor_generator_pb2'

when I enter
protoc object_detection/protos/*.proto --python_out=.
no error occures.
What should I do?