def _make_case_insensitive(value):
    """Replace the first character of a string by an uppercase-lowercase
    regex.

    Parameters
    ----------
    value : str
        Value (ex: "Residential").

    Returns
    -------
    value : str
        Output value (ex: "[rR]esidential").
    """
    return f'[{ value[0].lower() }{ value[0].upper() }]{ value[1:] }'