def delete_metadata_at_key(self, key):
j, r = self.datacenter.request('<STR_LIT>', self.path + '<STR_LIT>' + <EOL>key)<EOL>r.raise_for_status()<EOL>return self.get_metadata()<EOL>
::

    DELETE /:login/machines/:id/metadata/:key

:param key: identifier for matadata entry
:type key: :py:class:`basestring`

:Returns: current metadata
:rtype: :py:class:`dict`

Deletes the machine metadata contained at 'key'. Also explicitly 
requests and returns the machine metadata so that the local copy stays 
synchronized.