def METHOD_NAME(x):
    r"""
    Return the rational number ``x`` as a superscript.
    EXAMPLES::
        sage: from sage.typeset.unicode_art import unicode_superscript
        sage: unicode_superscript(15123902)
        '¹⁵¹²³⁹⁰²'
        sage: unicode_superscript(-712/5)
        '⁻⁷¹²ᐟ⁵'
    """
    return ''.join(_superscript_dict[i] for i in str(x))