def is_truetype_font(filepath):
    "Tests that a font has the TrueType file signature of either:\n         1) b'\x00\x01\x00\x00'\n         2) b'true' == 'true'"
    with open(filepath, 'rb') as f:
        file_signature = f.read(4)
        return file_signature in (b'\x00\x01\x00\x00', b'true')
