private com.google.protobuf.SingleFieldBuilderV3<
            com.google.cloud.vertexai.api.FunctionCallingConfig,
            com.google.cloud.vertexai.api.FunctionCallingConfig.Builder,
            com.google.cloud.vertexai.api.FunctionCallingConfigOrBuilder>
        getFunctionCallingConfigFieldBuilder() {
      if (functionCallingConfigBuilder_ == null) {
        functionCallingConfigBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.cloud.vertexai.api.FunctionCallingConfig,
                com.google.cloud.vertexai.api.FunctionCallingConfig.Builder,
                com.google.cloud.vertexai.api.FunctionCallingConfigOrBuilder>(
                getFunctionCallingConfig(), getParentForChildren(), isClean());
        functionCallingConfig_ = null;
      }
      return functionCallingConfigBuilder_;
    }
<pre>
Optional. Function calling config.
</pre>

<code>
.google.cloud.vertexai.v1.FunctionCallingConfig function_calling_config = 1 [(.google.api.field_behavior) = OPTIONAL];
</code>
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/ToolConfig.java