@java.lang.Override
  public boolean hasStartTime() {
    return ((bitField0_ & 0x00000001) != 0);
  }
<pre>
Start time of the span in nanoseconds from the UNIX epoch.
</pre>

<code>.google.protobuf.Timestamp start_time = 4;</code>

@return Whether the startTime field is set.
java-trace/proto-google-cloud-trace-v1/src/main/java/com/google/devtools/cloudtrace/v1/TraceSpan.java