'Remove an API callback.
The API callback chosen for removal is based on the
specificity of the provided JID+node combination.
See :meth:`~ApiRegistry.run` for more details.
:param string ctype: The name of the API to use.
:param string op: The API operation to perform.
:param JID jid: Optionally provide specific JID.
:param string node: Optionally provide specific node.'

def unregister(self, ctype, op, jid=None, node=None):

    self._setup(ctype, op)
    self.register(None, ctype, op, jid, node)
