':param message_number: String representing the number of a message
:type message_number: str
:raises ValueError: Thrown when one of the arguments are invalid'

def __init__(self, message_number):

    super(MessageNumber, self).__init__()
    if (not isinstance(message_number, str)):
        raise ValueError('Message    number    must    be    a    string')
    self._message_number = message_number
