public Builder clear() {
        super.clear();
        messageType_ = main.Messages.Message.MessageType.ExecutionStarting;
        bitField0_ = (bitField0_ & ~0x00000001);
        messageId_ = 0L;
        bitField0_ = (bitField0_ & ~0x00000002);
        if (executionStartingRequestBuilder_ == null) {
          executionStartingRequest_ = main.Messages.ExecutionStartingRequest.getDefaultInstance();
        } else {
          executionStartingRequestBuilder_.clear();
        }
        bitField0_ = (bitField0_ & ~0x00000004);
        if (specExecutionStartingRequestBuilder_ == null) {
          specExecutionStartingRequest_ = main.Messages.SpecExecutionStartingRequest.getDefaultInstance();
        } else {
          specExecutionStartingRequestBuilder_.clear();
        }
        bitField0_ = (bitField0_ & ~0x00000008);
        if (specExecutionEndingRequestBuilder_ == null) {
          specExecutionEndingRequest_ = main.Messages.SpecExecutionEndingRequest.getDefaultInstance();
        } else {
          specExecutionEndingRequestBuilder_.clear();
        }
        bitField0_ = (bitField0_ & ~0x00000010);
        if (scenarioExecutionStartingRequestBuilder_ == null) {
          scenarioExecutionStartingRequest_ = main.Messages.ScenarioExecutionStartingRequest.getDefaultInstance();
        } else {
          scenarioExecutionStartingRequestBuilder_.clear();
        }
        bitField0_ = (bitField0_ & ~0x00000020);
        if (scenarioExecutionEndingRequestBuilder_ == null) {
          scenarioExecutionEndingRequest_ = main.Messages.ScenarioExecutionEndingRequest.getDefaultInstance();
        } else {
          scenarioExecutionEndingRequestBuilder_.clear();
        }
        bitField0_ = (bitField0_ & ~0x00000040);
        if (executeStepRequestBuilder_ == null) {
          executeStepRequest_ = main.Messages.ExecuteStepRequest.getDefaultInstance();
        } else {
          executeStepRequestBuilder_.clear();
        }
        bitField0_ = (bitField0_ & ~0x00000080);
        if (executeStepResponseBuilder_ == null) {
          executeStepResponse_ = main.Messages.ExecuteStepResponse.getDefaultInstance();
        } else {
          executeStepResponseBuilder_.clear();
        }
        bitField0_ = (bitField0_ & ~0x00000100);
        if (executionEndingRequestBuilder_ == null) {
          executionEndingRequest_ = main.Messages.ExecutionEndingRequest.getDefaultInstance();
        } else {
          executionEndingRequestBuilder_.clear();
        }
        bitField0_ = (bitField0_ & ~0x00000200);
        if (stepValidateRequestBuilder_ == null) {
          stepValidateRequest_ = main.Messages.StepValidateRequest.getDefaultInstance();
        } else {
          stepValidateRequestBuilder_.clear();
        }
        bitField0_ = (bitField0_ & ~0x00000400);
        if (stepValidateResponseBuilder_ == null) {
          stepValidateResponse_ = main.Messages.StepValidateResponse.getDefaultInstance();
        } else {
          stepValidateResponseBuilder_.clear();
        }
        bitField0_ = (bitField0_ & ~0x00000800);
        if (executionStatusResponseBuilder_ == null) {
          executionStatusResponse_ = main.Messages.ExecutionStatusResponse.getDefaultInstance();
        } else {
          executionStatusResponseBuilder_.clear();
        }
        bitField0_ = (bitField0_ & ~0x00001000);
        return this;
      }