feat: add LangChainGo Huggingface backend (#446)

Co-authored-by: Ettore Di Giacinto <mudler@users.noreply.github.com>

pkg/langchain/langchain.go

@@ -0,0 +1,57 @@
+package langchain
+
+type PredictOptions struct {
+	Model string `json:"model"`
+	// MaxTokens is the maximum number of tokens to generate.
+	MaxTokens int `json:"max_tokens"`
+	// Temperature is the temperature for sampling, between 0 and 1.
+	Temperature float64 `json:"temperature"`
+	// StopWords is a list of words to stop on.
+	StopWords []string `json:"stop_words"`
+}
+
+type PredictOption func(p *PredictOptions)
+
+var DefaultOptions = PredictOptions{
+	Model:       "gpt2",
+	MaxTokens:   200,
+	Temperature: 0.96,
+	StopWords:   nil,
+}
+
+type Predict struct {
+	Completion string
+}
+
+func SetModel(model string) PredictOption {
+	return func(o *PredictOptions) {
+		o.Model = model
+	}
+}
+
+func SetTemperature(temperature float64) PredictOption {
+	return func(o *PredictOptions) {
+		o.Temperature = temperature
+	}
+}
+
+func SetMaxTokens(maxTokens int) PredictOption {
+	return func(o *PredictOptions) {
+		o.MaxTokens = maxTokens
+	}
+}
+
+func SetStopWords(stopWords []string) PredictOption {
+	return func(o *PredictOptions) {
+		o.StopWords = stopWords
+	}
+}
+
+// NewPredictOptions Create a new PredictOptions object with the given options.
+func NewPredictOptions(opts ...PredictOption) PredictOptions {
+	p := DefaultOptions
+	for _, opt := range opts {
+		opt(&p)
+	}
+	return p
+}