def collection_2_listed_string(elems):
    """
    Given a Container (i.e. a Set, List, etc.) of strings, 
    returns an HTML string wherein each item has its own line, and all items are in alphabetical order.

    This will be used to help format and contsruct the email text body (as an HTML)
    in the build_email_msg function.
    """

    # if the set is empty, output that no appointments are available
    if not elems:
        return 'None Available' + '<br>'

    # Initialize emtpy string
    string = ""  

    # Sorts the set (converts to a list)
    sort = sorted(elems)

     # Loop over each city in the set and append the city to the HTML string
    for city in sort:                  
        string += city + '<br>'   

    # Returns the HTML string of a list of cities
    return string