code: def setup_top(self):
          
          self.top_grammar = SchemaNode("grammar")
          self.top_grammar.attr = {
              "xmlns": "http://relaxng.org/ns/structure/1.0",
              "datatypeLibrary": "http://www.w3.org/2001/XMLSchema-datatypes"}
          self.tree = SchemaNode("start")
docs: Create top-level elements of the hybrid schema.