private void buildPartialRepeatedFields(com.google.devtools.cloudtrace.v1.Trace result) {
      if (spansBuilder_ == null) {
        if (((bitField0_ & 0x00000004) != 0)) {
          spans_ = java.util.Collections.unmodifiableList(spans_);
          bitField0_ = (bitField0_ & ~0x00000004);
        }
        result.spans_ = spans_;
      } else {
        result.spans_ = spansBuilder_.build();
      }
    }
<pre>
A trace describes how long it takes for an application to perform an
operation. It consists of a set of spans, each of which represent a single
timed event within the operation.
</pre>

Protobuf type {@code google.devtools.cloudtrace.v1.Trace}
java-trace/proto-google-cloud-trace-v1/src/main/java/com/google/devtools/cloudtrace/v1/Trace.java