src/Zipkin/RealSpan.php
public function setKind(string $kind): void
    {
        $this->recorder->setKind($this->traceContext, $kind);
    }
public function setKind(string $kind): void
    {
        $this->recorder->setKind($this->traceContext, $kind);
    }
The kind of span is optional. When set, it affects how a span is reported. For example, if the
kind is {@link Zipkin\Kind\SERVER}, the span's start timestamp is implicitly annotated as "sr"
and that plus its duration as "ss".

@param string $kind
@return void