docs: def add_key(self, key_name, private):
          """
          Add a new key to mist.io
  
          :param key_name: Name of the new key (it will be used as the key's id as well).
          :param private: Private ssh-key in string format (see also generate_key() ).
  
          :returns: An updated list of added keys.
          """
          payload = {
              'name': key_name,
              'priv': private
          }
  
          data = json.dumps(payload)
  
          req = self.request(self.uri + '/keys', data=data)
          response = req.put().json()
  
          self.update_keys()
          return response