public com.google.cloud.vertexai.api.ContentOrBuilder getSystemInstructionOrBuilder() {
      if (systemInstructionBuilder_ != null) {
        return systemInstructionBuilder_.getMessageOrBuilder();
      } else {
        return systemInstruction_ == null
            ? com.google.cloud.vertexai.api.Content.getDefaultInstance()
            : systemInstruction_;
      }
    }
<pre>
Optional. The user provided system instructions for the model.
Note: only text should be used in parts and content in each part will be in
a separate paragraph.
</pre>

<code>
optional .google.cloud.vertexai.v1.Content system_instruction = 8 [(.google.api.field_behavior) = OPTIONAL];
</code>
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/GenerateContentRequest.java