code: def set(self, field, value):
          
          if field == 'uuid':
              raise ValueError('uuid cannot be set')
          elif field == 'key':
              raise ValueError(
                  'key cannot be set. Use \'reset_key\' method')
          else:
              self.data[field] = value
docs: Sets the value of an app field.
  
          :param str field:
              The name of the app field. Trying to set immutable fields
              ``uuid`` or ``key`` will raise a ValueError.
          :param value:
              The new value of the app field.
          :raises: ValueError