code: def node(self, name, label=None, _attributes=None, **attrs):
          
          name = self._quote(name)
          attr_list = self._attr_list(label, attrs, _attributes)
          line = self._node % (name, attr_list)
          self.body.append(line)
docs: Create a node.
  
          Args:
              name: Unique identifier for the node inside the source.
              label: Caption to be displayed (defaults to the node ``name``).
              attrs: Any additional node attributes (must be strings).