def mapped_opts(v):
    """
    Used internally when creating a string of options to pass to
    Maxima.

    INPUT:

    - ``v`` - an object

    OUTPUT: a string.

    The main use of this is to turn Python bools into lower case
    strings.

    EXAMPLES::

        sage: sage.calculus.calculus.mapped_opts(True)
        'true'
        sage: sage.calculus.calculus.mapped_opts(False)
        'false'
        sage: sage.calculus.calculus.mapped_opts('bar')
        'bar'
    """
    if isinstance(v, bool):
        return str(v).lower()
    return str(v)