class_docstr: To run: "python -m saliency.core.gradients_test" from the top-level directory.
code: def gradient_fn(self, arr):
      # f(x,y,z) = 5x + y^2, sin(z)
      # d(f(x,y,z)) = [5, 2y, cos(z)]
      return np.array([5, 2 * arr[1], np.cos(arr[2])])
  
file_path: saliency/saliency/core/gradients_test.py
imports: import unittest
  import unittest.mock
  from .base import INPUT_OUTPUT_GRADIENTS
  from .base import SHAPE_ERROR_MESSAGE
  from .None import gradients
  import numpy
label_desc: Use image node_id 1 for calling the GradientSaliencyTest obj's underlying member method code with example usage: obj.gradient_fn(arr) and returns: np