def usage():
    """Return string detailing how this program is used."""

    return '''
    A Command Line Interface (CLI) program to send email.
    If the value to an argument is a file path and the file exists, the file
    will be read line by line and the values in the file will be used.
    When supplying multiple email addresses as an argument, a comma should be
    used to separate them.
    Arguments with spaces should be encolsed in double quotes (").'''
Return string detailing how this program is used.
recipes/Python/576807_Send_Email/recipe-576807.py