add support for examples to title chain

- added module doc with examples
- support providing examples for consistency

closes #163

lib/chains/text_to_title_chain.ex

@@ -2,6 +2,48 @@ defmodule LangChain.Chains.TextToTitleChain do
   @moduledoc """
   A convenience chain for turning a user's prompt text into a summarized title
   for the anticipated conversation.
+
+  ## Examples
+  A basic example that generates a title
+
+      llm = ChatOpenAI.new!(%{model: "gpt-3.5-turbo", stream: false, seed: 0})
+      user_text = "Let's start a new blog post about the magical properties of pineapple cookies."
+
+      %{
+        llm: llm,
+        input_text: user_text
+      }
+      |> TextToTitleChain.new!()
+      |> TextToTitleChain.evaluate()
+
+      #=> "Magical Properties of Pineapple Cookies Blog Post"
+
+  Want to get more consistent titles?
+
+  LLMs are pretty bad at following instructions for text length. However, we can
+  provide examples titles for the LLM to follow in format style and length. We
+  get the added benefit of getting more consistently formatted titles.
+
+  This is the same example, however now we provide other title examples to the
+  LLM to follow for consistency.
+
+     llm = ChatOpenAI.new!(%{model: "gpt-3.5-turbo", stream: false, seed: 0})
+      user_text = "Let's start a new blog post about the magical properties of
+      pineapple cookies."
+
+      %{
+        llm: llm,
+        input_text: user_text,
+        examples: [
+          "Blog Post: Making Delicious and Healthy Smoothies",
+          "System Email: Notifying Users of Planned Downtime"
+        ]
+      }
+      |> TextToTitleChain.new!()
+      |> TextToTitleChain.evaluate()
+
+      #=> "Blog Post: Exploring the Magic of Pineapple Cookies"
+
   """
   use Ecto.Schema
   import Ecto.Changeset
@@ -10,7 +52,6 @@ defmodule LangChain.Chains.TextToTitleChain do
   alias __MODULE__
   alias LangChain.Chains.LLMChain
   alias LangChain.LangChainError
-  alias LangChain.Message
   alias LangChain.Utils
   alias LangChain.Utils.ChainResult
 
@@ -19,12 +60,13 @@ defmodule LangChain.Chains.TextToTitleChain do
     field :llm, :any, virtual: true
     field :input_text, :string
     field :fallback_title, :string, default: "New topic"
+    field :examples, {:array, :string}, default: []
     field :verbose, :boolean, default: false
   end
 
   @type t :: %TextToTitleChain{}
 
-  @create_fields [:llm, :input_text, :fallback_title, :verbose]
+  @create_fields [:llm, :input_text, :fallback_title, :examples, :verbose]
   @required_fields [:llm, :input_text]
 
   @doc """
@@ -86,15 +128,22 @@ defmodule LangChain.Chains.TextToTitleChain do
   def run(%TextToTitleChain{} = chain, opts \\ []) do
     messages =
       [
-        Message.new_system!(
-          "You expertly summarize a user's prompt into a short title or phrase to represent a conversation."
-        ),
+        PromptTemplate.new!(%{
+          role: :system,
+          text: """
+          You expertly summarize the User Text into a short title or phrase to represent a conversation.
+
+          <%= if @examples != [] do %>Follow the style, approximate length, and format of the following examples:
+          <%= for example <- @examples do %>- <%= example %>
+          <% end %><% end %>
+          """
+        }),
         PromptTemplate.new!(%{
           role: :user,
-          text: "Generate and return the title and nothing else. Prompt:\n<%= @input %>"
+          text: "Generate and return the title and nothing else. User Text:\n<%= @input %>"
         })
       ]
-      |> PromptTemplate.to_messages!(%{input: chain.input_text})
+      |> PromptTemplate.to_messages!(%{input: chain.input_text, examples: chain.examples})
 
     %{llm: chain.llm, verbose: chain.verbose}
     |> LLMChain.new!()

test/chains/text_to_title_chain_test.exs

@@ -94,5 +94,27 @@ defmodule LangChain.Chains.TextToTitleChainTest do
 
       assert fallback_title == TextToTitleChain.evaluate(title_chain)
     end
+
+    @tag live_call: true, live_open_ai: true
+    test "supports using examples", %{llm: llm, input_text: input_text} do
+      data = %{
+        llm: llm,
+        input_text: input_text,
+        fallback_title: "Default new title",
+        examples: [
+          "Blog Post: Making Delicious and Healthy Smoothies",
+          "System Email: Notifying Users of Planned Downtime"
+        ],
+        verbose: true
+      }
+
+      result_title =
+        data
+        |> TextToTitleChain.new!()
+        |> TextToTitleChain.evaluate()
+
+      assert String.starts_with?(result_title, "Blog Post:")
+      assert String.contains?(result_title, "Pineapple")
+    end
   end
 end