genai: add SystemInstruction (#84)

Author: jba

genai/client.go

@@ -105,7 +105,10 @@ type GenerativeModel struct {
 	GenerationConfig
 	SafetySettings []*SafetySetting
 	Tools          []*Tool
-	ToolConfig     *ToolConfig
+	ToolConfig     *ToolConfig // configuration for tools
+	// SystemInstruction (also known as "system prompt") is a more forceful prompt to the model.
+	// The model will adhere the instructions more strongly than if they appeared in a normal prompt.
+	SystemInstruction *Content
 }
 
 // GenerativeModel creates a new instance of the named generative model.
@@ -165,12 +168,13 @@ func (m *GenerativeModel) generateContent(ctx context.Context, req *pb.GenerateC
 
 func (m *GenerativeModel) newGenerateContentRequest(contents ...*Content) *pb.GenerateContentRequest {
 	return &pb.GenerateContentRequest{
-		Model:            m.fullName,
-		Contents:         support.TransformSlice(contents, (*Content).toProto),
-		SafetySettings:   support.TransformSlice(m.SafetySettings, (*SafetySetting).toProto),
-		Tools:            support.TransformSlice(m.Tools, (*Tool).toProto),
-		ToolConfig:       m.ToolConfig.toProto(),
-		GenerationConfig: m.GenerationConfig.toProto(),
+		Model:             m.fullName,
+		Contents:          support.TransformSlice(contents, (*Content).toProto),
+		SafetySettings:    support.TransformSlice(m.SafetySettings, (*SafetySetting).toProto),
+		Tools:             support.TransformSlice(m.Tools, (*Tool).toProto),
+		ToolConfig:        m.ToolConfig.toProto(),
+		GenerationConfig:  m.GenerationConfig.toProto(),
+		SystemInstruction: m.SystemInstruction.toProto(),
 	}
 }
 

genai/example_test.go

@@ -59,6 +59,9 @@ func ExampleGenerativeModel_GenerateContent_config() {
 	model.SetTopP(0.5)
 	model.SetTopK(20)
 	model.SetMaxOutputTokens(100)
+	model.SystemInstruction = &genai.Content{
+		Parts: []genai.Part{genai.Text("You are Yoda from Star Wars.")},
+	}
 	resp, err := model.GenerateContent(ctx, genai.Text("What is the average size of a swallow?"))
 	if err != nil {
 		log.Fatal(err)