public Builder mergeScheduleTime(com.google.protobuf.Timestamp value) {
      if (scheduleTimeBuilder_ == null) {
        if (((bitField0_ & 0x00000002) != 0)
            && scheduleTime_ != null
            && scheduleTime_ != com.google.protobuf.Timestamp.getDefaultInstance()) {
          getScheduleTimeBuilder().mergeFrom(value);
        } else {
          scheduleTime_ = value;
        }
      } else {
        scheduleTimeBuilder_.mergeFrom(value);
      }
      if (scheduleTime_ != null) {
        bitField0_ |= 0x00000002;
        onChanged();
      }
      return this;
    }
<pre>
Required. The task's current schedule time, available in the
[schedule_time][google.cloud.tasks.v2beta2.Task.schedule_time] returned by
[LeaseTasks][google.cloud.tasks.v2beta2.CloudTasks.LeaseTasks] response or
[RenewLease][google.cloud.tasks.v2beta2.CloudTasks.RenewLease] response.
This restriction is to ensure that your worker currently holds the lease.
</pre>

<code>.google.protobuf.Timestamp schedule_time = 2 [(.google.api.field_behavior) = REQUIRED];
</code>
java-tasks/proto-google-cloud-tasks-v2beta2/src/main/java/com/google/cloud/tasks/v2beta2/AcknowledgeTaskRequest.java