code: def get(identifier, value=None):
    
    if value is None:
      value = identifier
    if identifier is None:
      return None
    elif isinstance(identifier, dict):
      try:
        return deserialize(identifier)
      except ValueError:
        return value
    elif isinstance(identifier, six.string_types):
      config = {'class_name': str(identifier), 'config': {}}
      try:
        return deserialize(config)
      except ValueError:
        return value
    elif callable(identifier):
      return identifier
    return value
docs: Getter for loading from strings; returns value if can't load.