code: def gradient_RGBa(self):
      return Image.merge(
          "RGBa",
          [
              self.gradient_L,
              self.gradient_L.transpose(Image.Transpose.ROTATE_90),
              self.gradient_L.transpose(Image.Transpose.ROTATE_180),
              self.gradient_L.transpose(Image.Transpose.ROTATE_270),
          ],
      )
  
imports: from __future__ import annotations
  import pytest
  from PIL import Image
  from .helper import CachedProperty, assert_image_equal
label_desc: Use image node_id 9 for calling the TestImagingPaste obj's underlying member method code with example usage: obj.gradient_RGBa() and returns: Image