code: def _handle_child(
              self, node: SchemaNode, stmt: Statement, sctx: SchemaContext) -> None:
          
          if not sctx.schema_data.if_features(stmt, sctx.text_mid):
              return
          node.name = stmt.argument
          node.ns = sctx.default_ns
          node._get_description(stmt)
          self._add_child(node)
          node._handle_substatements(stmt, sctx)
docs: Add child node to the receiver and handle substatements.