Get all tags related to a given port.

        This is the inverse of what is stored in self.cluster_tags).

def get_tags_of_port(self, port):
        """
        Get all tags related to a given port.

        This is the inverse of what is stored in self.cluster_tags).
        """
        return(sorted([tag for tag in self.cluster_tags
                       if port in self.cluster_tags[tag]]))