code: def create_roots(self, yam):
          
          self.local_grammar = SchemaNode("grammar")
          self.local_grammar.attr = {
              "ns": yam.search_one("namespace").arg,
              "nma:module": self.module.arg}
          src_text = "YANG module '%s'" % yam.arg
          revs = yam.search("revision")
          if len(revs) > 0:
              src_text += " revision %s" % self.current_revision(revs)
          self.dc_element(self.local_grammar, "source", src_text)
          start = SchemaNode("start", self.local_grammar)
          self.data = SchemaNode("nma:data", start, interleave=True)
          self.data.occur = 2
          self.rpcs = SchemaNode("nma:rpcs", start, interleave=False)
          self.notifications = SchemaNode("nma:notifications", start,
                                          interleave=False)
docs: Create the top-level structure for module `yam`.