code: def create_child_folder(self, folder_name):
          
  
          if not folder_name:
              return None
  
          if self.root:
              url = self.build_url(self._endpoints.get('root_folders'))
          else:
              url = self.build_url(
                  self._endpoints.get('child_folders').format(id=self.folder_id))
  
          response = self.con.post(url,
                                   data={self._cc('displayName'): folder_name})
          if not response:
              return None
  
          folder = response.json()
  
          # Everything received from cloud must be passed as self._cloud_data_key
          return self.__class__(parent=self, **{self._cloud_data_key: folder})
docs: Creates a new child folder
  
          :param str folder_name: name of the new folder to create
          :return: newly created folder
          :rtype: ContactFolder or None