_on_step_end function. The tensors specified in the list
will be passed as callback_kwargs argument. You will only be able to include variables listed in the
._callback_tensor_inputs attribute of your pipeine class.   Returns 
StableDiffusionPipelineOutput or tuple
  
StableDiffusionPipelineOutput if return_dict is True, otherwise a tuple
containing the output images.
  Function invoked when calling the pipeline for generation.  Examples:   Cop