def location_modifier(fields):
    """
    Modify the parsed location variable.

    Subtract 1 from all the start positions in order to be able to use pd.read_fwf()

    Parameters:
        field (list): The list of tuples created by location_parser()

    Returns:
        fields: A list of tuples
    """
    for i, item in enumerate(fields):
        item[0] = item[0] - 1
        fields[i] = tuple(item)
    return fields