code: def _uses_stmt(self, stmt: Statement, sctx: SchemaContext) -> None:
          
          if not sctx.schema_data.if_features(stmt, sctx.text_mid):
              return
          grp, gid = sctx.schema_data.get_definition(stmt, sctx)
          if stmt.find1("when"):
              sn = GroupNode()
              self._add_child(sn)
          else:
              sn = self
          sn._handle_substatements(grp, gid)
          for augst in stmt.find_all("augment"):
              sn._augment_stmt(augst, sctx)
          for refst in stmt.find_all("refine"):
              sn._refine_stmt(refst, sctx)
docs: Handle uses statement.