private com.google.protobuf.SingleFieldBuilderV3<
            com.google.cloud.vertexai.api.FunctionCall,
            com.google.cloud.vertexai.api.FunctionCall.Builder,
            com.google.cloud.vertexai.api.FunctionCallOrBuilder>
        getFunctionCallFieldBuilder() {
      if (functionCallBuilder_ == null) {
        if (!(dataCase_ == 5)) {
          data_ = com.google.cloud.vertexai.api.FunctionCall.getDefaultInstance();
        }
        functionCallBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.cloud.vertexai.api.FunctionCall,
                com.google.cloud.vertexai.api.FunctionCall.Builder,
                com.google.cloud.vertexai.api.FunctionCallOrBuilder>(
                (com.google.cloud.vertexai.api.FunctionCall) data_,
                getParentForChildren(),
                isClean());
        data_ = null;
      }
      dataCase_ = 5;
      onChanged();
      return functionCallBuilder_;
    }
<pre>
Optional. A predicted [FunctionCall] returned from the model that
contains a string representing the [FunctionDeclaration.name] with the
parameters and their values.
</pre>

<code>
.google.cloud.vertexai.v1.FunctionCall function_call = 5 [(.google.api.field_behavior) = OPTIONAL];
</code>
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/Part.java