code: def _alpha_blend_background(ctable, background_color):
      alphas = ctable[:, -1][:, np.newaxis] / 255.0
      use_table = ctable.copy()
      use_table[:, -1] = 255.0
      return (use_table * alphas) + background_color * (1 - alphas)
  
imports: import collections.abc
  import functools
  import os
  import platform
  import signal
  import sys
  from colorsys import rgb_to_hls
  from contextlib import contextmanager
  from ctypes import c_char_p, c_void_p, cdll
  from pathlib import Path
  import numpy
  from ...fixes import _compare_version
  from ...utils import _check_qt_version, _validate_type, logger, warn
  from ..utils import _get_cmap
label_desc: Use image node_id 3 for calling a global function with example usage: _alpha_blend_background(ctable, background_color) and returns: unknown