'Return ``postfetch_cols()`` from the underlying
:class:`.ExecutionContext`.
See :class:`.ExecutionContext` for details.
Raises :class:`~sqlalchemy.exc.InvalidRequestError` if the executed
statement is not a compiled expression construct
or is not an insert() or update() construct.'

def postfetch_cols(self):

    if (not self.context.compiled):
        raise exc.InvalidRequestError('Statement    is    not    a    compiled    expression    construct.')
    elif ((not self.context.isinsert) and (not self.context.isupdate)):
        raise exc.InvalidRequestError('Statement    is    not    an    insert()    or    update()    expression    construct.')
    return self.context.postfetch_cols
