code: def describe(value):
      
      if isinstance(value, types.ModuleType):
          return describe_file(value)
      elif isinstance(value, messages.Field):
          return describe_field(value)
      elif isinstance(value, messages.Enum):
          return describe_enum_value(value)
      elif isinstance(value, type):
          if issubclass(value, messages.Message):
              return describe_message(value)
          elif issubclass(value, messages.Enum):
              return describe_enum(value)
      return None
docs: Describe any value as a descriptor.
  
      Helper function for describing any object with an appropriate descriptor
      object.
  
      Args:
        value: Value to describe as a descriptor.
  
      Returns:
        Descriptor message class if object is describable as a descriptor, else
        None.