code: def get_key(self, name, attr_type, scope, default):
      keys_key = (name, attr_type, scope)
      try:
          return self.keys[keys_key]
      except KeyError:
          if self.named_key_ids:
              new_id = name
          else:
              new_id = f"d{len(list(self.keys))}"
  
          self.keys[keys_key] = new_id
          key_kwargs = {
              "id": new_id,
              "for": scope,
              "attr.name": name,
              "attr.type": attr_type,
          }
          key_element = self.myElement("key", **key_kwargs)
          # add subelement for data default value if present
          if default is not None:
              default_element = self.myElement("default")
              default_element.text = str(default)
              key_element.append(default_element)
          self.xml.insert(0, key_element)
      return new_id
  
imports: import warnings
  from collections import defaultdict
  import networkx
  from networkx.utils import open_file
label_desc: Use image node_id 4 for calling the GraphMLWriter obj's underlying member method code with example usage: obj.get_key(name, attr_type, scope, default) and returns: new_id, self