code: def diff(x, axis=-1):
      """Take the finite difference of a tensor along an axis.
  
      Args:
        x: Input tensor of any dimension.
        axis: Axis on which to take the finite difference.
  
      Returns:
        d: Tensor with size less than x by 1 along the difference dimension.
  
      Raises:
        ValueError: Axis out of range for tensor.
      """
      shape = x.get_shape()
      if axis >= len(shape):
          raise ValueError(
              "Invalid axis index: %d for tensor with only %d axes."
              % (axis, len(shape))
          )
  
      begin_back = [0 for unused_s in range(len(shape))]
      begin_front = [0 for unused_s in range(len(shape))]
      begin_front[axis] = 1
  
      size = shape.as_list()
      size[axis] -= 1
      slice_front = tf.slice(x, begin_front, size)
      slice_back = tf.slice(x, begin_back, size)
      d = slice_front - slice_back
      return d
  
file_path: magenta/magenta/models/gansynth/lib/spectral_ops.py
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import numpy
  import tensorflow.compat.v1
label_desc: Use image node_id 4 for calling a global function with example usage: diff(x, axis) and returns: d