Given a ParsedNodePatch, add the new information to the node.

def patch(self, patch):
        """Given a ParsedNodePatch, add the new information to the node."""
        # explicitly pick out the parts to update so we don't inadvertently
        # step on the model name or anything
        self._contents.update({
            'patch_path': patch.original_file_path,
            'description': patch.description,
            'columns': patch.columns,
            'docrefs': patch.docrefs,
        })
        # patches always trigger re-validation
        self.validate()