code: def clone_for(self, other_instance, memo=None):
          
  
          if memo is None:
              result = copy.deepcopy(self)
          else:
              result = copy.deepcopy(self, memo)
          result.instance = other_instance
          return result
docs: Clone this bound field for another instance, possibly during a
          :func:`~copy.deepcopy` operation.
  
          :param other_instance: Another form instance to which the newly created
                                 bound field shall be bound.
          :type other_instance: :class:`object`
          :param memo: Optional deepcopy-memo (see :mod:`copy` for details)
  
          If this is called during a deepcopy operation, passing the `memo` helps
          preserving and preventing loops. This method is essentially a
          deepcopy-operation, with a modification of the :attr:`instance`
          afterwards.