code: def test_overlay_onto_background_image(self):
      self.evaluate_function(
          imaugs.overlay_onto_background_image,
          background_image=EMOJI_PATH,
          overlay_size=0.5,
          scale_bg=True,
      )
  
imports: import unittest
  from augly import image
  from augly.tests.image_tests.base_unit_test import BaseImageUnitTest
  from augly.utils import EMOJI_PATH, IMG_MASK_PATH
  from PIL import Image
label_desc: Use image node_id 19 for calling the FunctionalImageUnitTest obj's underlying member method code with example usage: obj.test_overlay_onto_background_image() without return types