<gh_stars>0
import os

c.NotebookApp.tornado_settings = {
    "headers": {
        "Content-Security-Policy": "frame-ancestors self %s"
        % os.getenv("FRAME_ANCESTORS", "")
    }
}

import os

c.NotebookApp.tornado_settings = {
    "headers": {
        "Content-Security-Policy": "frame-ancestors self %s"
        % os.getenv("FRAME_ANCESTORS", "")
    }
}