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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def recover_buildpack(app_folder):
 """ Given the path to an app folder where an app was just built, return a BuildPack object pointing to the dir for the buildpack used during the build. Relies on the builder.sh script storing the buildpack location in /.buildpack inside the container. """

    filepath = os.path.join(app_folder, '.buildpack')
    with open(filepath) as f:
        buildpack_picked = f.read()
    buildpack_picked = buildpack_picked.lstrip('/')
    buildpack_picked = buildpack_picked.rstrip('\n')
    buildpack_picked = os.path.join(os.getcwd(), buildpack_picked)
    return BuildPack(buildpack_picked)