def convert_string(string):
    """Convert string to int, float or bool.
    """
    if is_int(string):
        return int(string)
    elif is_float(string):
        return float(string)
    elif convert_bool(string)[0]:
        return convert_bool(string)[1]
    elif string == 'None':
        return None
    else:
        return string
Convert string to int, float or bool.