code: def blit(im1, im2, pos=None, mask=None):
      """Blit an image over another.
  
      Blits ``im1`` on ``im2`` as position ``pos=(x,y)``, using the
      ``mask`` if provided.
      """
      if pos is None:
          pos = (0, 0)  # pragma: no cover
      else:
          # Cast to tuple in case pos is not subscriptable.
          pos = tuple(pos)
      im2.paste(im1, pos, mask)
      return im2
  
imports: import numpy
label_desc: Use image node_id 1 for calling a global function with example usage: blit(im1, im2, pos, mask) and returns: im2