'Create a shallow copy of this ClauseElement.
This method may be used by a generative API.  Its also used as
part of the "deep" copy afforded by a traversal that combines
the _copy_internals() method.'

def _clone(self):

    c = self.__class__.__new__(self.__class__)
    c.__dict__ = self.__dict__.copy()
    ClauseElement._cloned_set._reset(c)
    ColumnElement.comparator._reset(c)
    c._is_clone_of = self
    return c
