def file_read_file_location_mod(mod_file, mod_dict={}):
    """
    read the file that lists by file location modification lookups
    note: file location is the file dirname w/o leading common drive folders 
    
    file format:
            new_label\tfile location
    previously known to be saved to:
        os.path.join(output_path, 'location_set_mapping.tab')

    Args:
        mod_file (str): filename path to location_set_mapping.tab
        mod_dict (dict): the modification dictionary to add the content read
            from the file to; directory vs file location label
    Returns:
        mod_dict (dict) whose keys are addresses and values are a label list
    """
    with open(mod_file) as fHan:
        file_loc_mod_lines = fHan.readlines()
    
        for line in file_loc_mod_lines:
            try:
                line = line.strip('\n')
                new_label, loc_to_mod = line.split('\t')
            except ValueError:  # occurs if line above is improperly formatted
                continue
            mod_dict[loc_to_mod] = [new_label]
       
    return(mod_dict)