func (t *Tracer) Log(key string, value interface{}) {
	t.Last().LogKV(key, value)
}
func (t *Tracer) Log(key string, value interface{}) {
	t.Last().LogKV(key, value)
}
func ( t * Tracer ) Log ( key string , value interface { } ) { t . Last ( ) . LogKV ( key , value ) }
// Log adds a log to the last pushed span.
Log adds a log to the last pushed span .