def METHOD_NAME(self, key, value='', dry_run=False):
    """
    Add a tag to this object.  Tags are stored by AWS and can be used
    to organize and filter resources.  Adding a tag involves a round-trip
    to the EC2 service.
    :type key: str
    :param key: The key or name of the tag being stored.
    :type value: str
    :param value: An optional value that can be stored with the tag.
                  If you want only the tag name and no value, the
                  value should be the empty string.
    """
    self.add_tags({key: value}, dry_run)