herwise a tuple is
returned where the first element is a list with the generated images.
  The call function to the pipeline for generation.  truncate  < source > ( log_p_x_0: FloatTensor truncation_rate: float  )    Truncates log_p_x_0 such that for each column vector, the total cumulative probability is truncation_rate
The lowest probabilities that would increase the cumulative probability above truncation_rate are set to
zero.  ImagePipeline