def delete_metadata_at_key(self, key):
        """
        ::
        
            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.
        """
        j, r = self.datacenter.request('DELETE', self.path + '/metadata/' + 
                    key)
        r.raise_for_status()
        return self.get_metadata()