code: def value(self):
          
          try:
              return self._value
          except AttributeError:
              self._value = self.field.default()
              return self._value
docs: The current value of the field. If no value is set when this attribute
          is accessed for reading, the :meth:`default` of the field is invoked
          and the result is set and returned as value.
  
          Only values contained in the :attr:`~.BoundOptionsField.options` can be
          set, other values are rejected with a :class:`ValueError`. To revert
          the value to the default value specified in the descriptor, use the
          ``del`` operator.