final public function upsert(TagKey $key, TagValue $value)
    {
        $this->m[$key->getName()] = new Tag($key, $value);
    }
final public function upsert(TagKey $key, TagValue $value)
    {
        $this->m[$key->getName()] = new Tag($key, $value);
    }
final public function upsert ( TagKey $ key , TagValue $ value ) { $ this -> m [ $ key -> getName ( ) ] = new Tag ( $ key , $ value ) ; }
Insert or Update a Tag into TagContext given provided TagKey with
provided string value.

@param TagKey $key key of the Tag.
@param TagValue $value value of the Tag.
Insert or Update a Tag into TagContext given provided TagKey with provided string value .