'Returns the list of all valid entries for the argument of
``TextClip`` given (can be ``font``, ``color``, etc...)'

@staticmethod
def list(arg):

    popen_params = {'stdout': sp.PIPE, 'stderr': DEVNULL, 'stdin': DEVNULL}
    if (os.name == 'nt'):
        popen_params['creationflags'] = 134217728
    process = sp.Popen([get_setting('IMAGEMAGICK_BINARY'), '-list', arg], **popen_params)
    result = process.communicate()[0]
    lines = result.splitlines()
    if (arg == 'font'):
        return [l.decode('UTF-8')[8:] for l in lines if l.startswith('        Font:')]
    elif (arg == 'color'):
        return [l.split('    ')[0] for l in lines[2:]]
    else:
        raise Exception("Moviepy:Error!    Argument    must    equal    'font'    or    'color'")
