public static Builder newBuilder(com.google.devtools.cloudtrace.v2.Span prototype) {
    return DEFAULT_INSTANCE.toBuilder().mergeFrom(prototype);
  }
<pre>
Optional. Distinguishes between spans generated in a particular context.
For example, two spans with the same name may be distinguished using
`CLIENT` (caller) and `SERVER` (callee) to identify an RPC call.
</pre>

<code>
.google.devtools.cloudtrace.v2.Span.SpanKind span_kind = 14 [(.google.api.field_behavior) = OPTIONAL];
</code>

@return The spanKind.
java-trace/proto-google-cloud-trace-v2/src/main/java/com/google/devtools/cloudtrace/v2/Span.java