Holoviews Bokeh cmap alpha not working

hv_cmap_alpha.ipynb

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   "source": [
    "import numpy as np\n",
    "\n",
    "import bokeh\n",
    "import holoviews as hv\n",
    "import xarray as xr\n",
    "import matplotlib.pyplot as plt\n",
    "import matplotlib\n"
   ]
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   "cell_type": "code",
   "execution_count": null,
   "id": "18451652-abe3-46de-9acc-90abf8387261",
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    "_cmap = plt.cm.RdBu\n",
    "cmap = _cmap(np.arange(_cmap.N))\n",
    "cmap[:,-1] = np.linspace(0, 1, _cmap.N)\n",
    "cmap = matplotlib.colors.ListedColormap(cmap)"
   ]
  },
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   "cell_type": "code",
   "execution_count": null,
   "id": "33046744-67c7-4812-bf26-34e1c49681f7",
   "metadata": {},
   "outputs": [],
   "source": [
    "hv.extension('matplotlib')\n",
    "\n",
    "ls = np.linspace(0, 10, 200)\n",
    "xx, yy = np.meshgrid(ls, ls)\n",
    "\n",
    "bounds=(-1,-1,1,1)   # Coordinate system: (left, bottom, right, top)\n",
    "img = hv.Image(np.sin(xx)*np.cos(yy), bounds=bounds).opts(cmap=cmap)\n",
    "img"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "6a3b6765-2b18-429f-924d-109422d9495f",
   "metadata": {},
   "outputs": [],
   "source": [
    "hv.extension('bokeh')\n",
    "\n",
    "ls = np.linspace(0, 10, 200)\n",
    "xx, yy = np.meshgrid(ls, ls)\n",
    "\n",
    "bounds=(-1,-1,1,1)   # Coordinate system: (left, bottom, right, top)\n",
    "img = hv.Image(np.sin(xx)*np.cos(yy), bounds=bounds).opts(cmap=cmap)\n",
    "img"
   ]
  }
 ],
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