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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 _load_manifest_from_file(manifest, path):
 """ load manifest from file """

    path = os.path.abspath(os.path.expanduser(path))
    if not os.path.exists(path):
        raise ManifestException("Manifest does not exist at {0}!".format(path))
    manifest.read(path)
    if not manifest.has_option('config', 'source'):
        manifest.set('config', 'source', str(path))