docs: func Build(req *request.Request) {
  	var buf []byte
  	var err error
  	if req.ParamsFilled() {
  		buf, err = jsonutil.BuildJSON(req.Params)
  		if err != nil {
  			req.Error = awserr.New("SerializationError", "failed encoding JSON RPC request", err)
  			return
  		}
  	} else {
  		buf = emptyJSON
  	}
  
  	if req.ClientInfo.TargetPrefix != "" || string(buf) != "{}" {
  		req.SetBufferBody(buf)
  	}
  
  	if req.ClientInfo.TargetPrefix != "" {
  		target := req.ClientInfo.TargetPrefix + "." + req.Operation.Name
  		req.HTTPRequest.Header.Add("X-Amz-Target", target)
  	}
  
  	// Only set the content type if one is not already specified and an
  	// JSONVersion is specified.
  	if ct, v := req.HTTPRequest.Header.Get("Content-Type"), req.ClientInfo.JSONVersion; len(ct) == 0 && len(v) != 0 {
  		jsonVersion := req.ClientInfo.JSONVersion
  		req.HTTPRequest.Header.Set("Content-Type", "application/x-amz-json-"+jsonVersion)
  	}
  }