def parse_font_awesome_icon(option):
    """
    Function that parses an argument related to the `icon` and `description`
    properties of `ipywidgets.Button`. If the provided option is an `str` that
    starts with `fa-`, then a font-awesome icon is assumed.

    Parameters
    ----------
    option : `str` or ``None``
        The selected `description` option.

    Returns
    -------
    icon : `str` or ``None``
        The selected icon option.
    description : `str` or ``None``
        The selected description option.
    """
    if option is None:
        icon = description = None
    elif len(option) > 3 and option[:3] == 'fa-':
        icon = option
        description = ''
    else:
        icon = None
        description = option
    return icon, description
