class_docstr: Provides common methods for a protocol buffer object.
  
  Wraps a single string value. This makes testing equality easy.
code: def FromString(string):  # pylint: disable=invalid-name
      return MockStringProto(string)
  
file_path: magenta/magenta/common/testing_lib.py
imports: import numpy
  import six
  from google.protobuf import text_format
label_desc: Use image node_id 2 for calling the MockStringProto obj's underlying member method code with example usage: obj.FromString(string) and returns: MockStringProto