docs: async def is_cn(self, client):
          """Return True if node at {base_url} is a CN, False if it is an MN.
  
          Raise a DataONEException if it's not a functional CN or MN.
  
          """
          node_pyxb = await client.get_capabilities()
          return d1_common.type_conversions.pyxb_get_type_name(node_pyxb) == "NodeList"