code: def EnumValueName(self, enum, value):
      
      return self.enum_types_by_name[enum].values_by_number[value].name
docs: Returns the string name of an enum value.
  
      This is just a small helper method to simplify a common operation.
  
      Args:
        enum: string name of the Enum.
        value: int, value of the enum.
  
      Returns:
        string name of the enum value.
  
      Raises:
        KeyError if either the Enum doesn't exist or the value is not a valid
          value for the enum.