'Remove a tag from this object.  Removing 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 a value is provided, it must match the value currently
stored in EC2.  If not, the tag will not be removed.  If
a value of None is provided, the tag will be
unconditionally deleted.
NOTE: There is an important distinction between a value
of \'\' and a value of None.'

def remove_tag(self, key, value=None, dry_run=False):

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