class_docstr: Representation class for `__shared__` annotations, which work as follows:
  
  - if `key` is set for the module in config file, its value will take
    precedence
  - if `key` is not set for the module but present in the config file, its
    value will be used
  - otherwise, use the provided `default_value` as fallback
  
  Args:
      key: config[key] will be injected
      default_value: fallback value
code: def __init__(self, key, default_value=None):
      super(SharedConfig, self).__init__()
      self.key = key
      self.default_value = default_value
  
imports: from __future__ import absolute_import
  from __future__ import print_function
  from __future__ import division
  import inspect
  import importlib
  import re
label_desc: Use image node_id 1 to create a new SharedConfig object from inherited base classes: object with example: obj = SharedConfig(key, default_value)