'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.'

def add_tag(self, key, value='', dry_run=False):

    self.add_tags({key: value}, dry_run)
