code: def get_child_progress(self, parent_min, parent_max):
          
          return SubProgressCallback(parent=self, parent_min=parent_min, parent_max=parent_max)
docs: Create a new child ProgressCallback.
          Minimum and maximum values of the child are mapped to parent_min and parent_max of this parent ProgressCallback.
          :param parent_min: minimum value of the child is mapped to parent_min of this parent ProgressCallback
          :param parent_max: maximum value of the child is mapped to parent_max of this parent ProgressCallback
          :return: instance of SubProgressCallback