code: def l1_distance(x1, x2):
      """Returns L1 distance between two points."""
      return np.abs(x1 - x2).sum()
  
file_path: saliency/saliency/core/guided_ig.py
imports: from .base import CoreSaliency
  from .base import INPUT_OUTPUT_GRADIENTS
  import math
  import numpy
label_desc: Use image node_id 1 for calling a global function with example usage: l1_distance(x1, x2) and returns: np