import re


def str_username(attending_username):
    """Determine if the input username is valid and meaningful

    Check if the attending's username contain any number and
    return corresponding results

    Args:
        attending_username(str): the username of target attending
    Returns:
        A string that states the attending's username is invalid
        due to the numeric elements it contains, or a bool
        variable True that indicates the username is valid.
    """
    if bool(re.search(r'\d', attending_username)) is False:
        return True
    else:
        return "Please enter a valid username string with no numbers!"