@staticmethod<EOL><INDENT>def _get_list_keys(schema_node):<DEDENT>
nodes = list(filter(lambda x: x.get('<STR_LIT>'),<EOL>schema_node.getchildren()))<EOL>return [n.tag for n in nodes]<EOL>
_get_list_keys

        Low-level api: Given a schema node, in particular, a list type schema
        node, it returns a list of keys.

        Parameters
        ----------

        schema_node : `Element`
            A schema node.

        Returns
        -------

        list
            A list of tags of keys in `{url}tagname` notation.