public boolean hasStartTime() {
          return ((bitField0_ & 0x00000002) != 0);
        }
<pre>
Optional. The starting timestamp for messages to import.
</pre>

<code>
.google.protobuf.Timestamp start_time = 2 [(.google.api.field_behavior) = OPTIONAL];
</code>

@return Whether the startTime field is set.
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/SlackSource.java