private com.google.protobuf.SingleFieldBuilderV3<
            com.google.protobuf.Struct,
            com.google.protobuf.Struct.Builder,
            com.google.protobuf.StructOrBuilder>
        getArgsFieldBuilder() {
      if (argsBuilder_ == null) {
        argsBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.protobuf.Struct,
                com.google.protobuf.Struct.Builder,
                com.google.protobuf.StructOrBuilder>(getArgs(), getParentForChildren(), isClean());
        args_ = null;
      }
      return argsBuilder_;
    }
<pre>
Optional. Required. The function parameters and values in JSON object
format. See [FunctionDeclaration.parameters] for parameter details.
</pre>

<code>.google.protobuf.Struct args = 2 [(.google.api.field_behavior) = OPTIONAL];</code>
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/FunctionCall.java