Iex help command not working

I am currently enrolled in the Pragmatic Studio Elixir & OTP course and have just completed the section on module attributes. I have the following code:

defmodule Servy.Handler do
  @moduledoc "Handles HTTP requests"

  @pages_path Path.expand("../../pages", __DIR__)

  @doc "Transforms the request into a response."
  def handle(request) do
    request
    |> parse
    |> rewrite_path
    |> log
    |> route
    |> track
    |> format_response
  end

  def emojify(%{status: 200} = conv) do
    body = ":) " <> conv.resp_body <> " :)"
    %{conv | resp_body: body}
  end

  def emojify(conv), do: conv

  def track(%{status: 404, path: path} = conv) do
    IO.puts("Warning: #{path} is on the loose!")
    conv
  end

  @doc "Logs 404 requests"
  def track(conv), do: conv

  def rewrite_path(%{path: "/wildlife"} = conv) do
    %{conv | path: "/wildthings"}
  end

  def rewrite_path(%{path: "/bears?id=" <> id} = conv) do
    %{conv | path: "/bears/#{id}"}
  end

  def rewrite_path(conv), do: conv

  def log(conv), do: IO.inspect(conv)

  def parse(request) do
    # TODO Parse the request string into a map
    [method, path, _] =
      request
      |> String.split("\n")
      |> List.first()
      |> String.split(" ")

    %{method: method, path: path, resp_body: "", status: nil}
  end

  def route(%{method: "GET", path: "/wildthings"} = conv) do
    %{conv | status: 200, resp_body: "Bears, Lions, Tigers"}
  end

  def route(%{method: "GET", path: "/bears"} = conv) do
    %{conv | status: 200, resp_body: "Teddy, Smokey, Paddington"}
  end

  def route(%{method: "GET", path: "/bears/new"} = conv) do
    @pages_path
    |> Path.join("form.html")
    |> File.read()
    |> handle_file(conv)
  end

  def route(%{method: "GET", path: "/bears/" <> id} = conv) do
    %{conv | status: 200, resp_body: "Bear #{id}"}
  end

  def route(%{method: "GET", path: "/pages/" <> file} = conv) do
    Path.expand("../../pages", __DIR__)
    |> Path.join(file <> ".html")
    |> File.read()
    |> handle_file(conv)
  end

  def route(%{method: "GET", path: "/about"} = conv) do
    Path.expand("../../pages", __DIR__)
    |> Path.join("about.html")
    |> File.read()
    |> handle_file(conv)
  end

  def route(%{method: "DELETE", path: "/bears/" <> _id} = conv) do
    %{conv | status: 403, resp_body: "Deleting a bear is forbidden!"}
  end

  def route(%{path: path} = conv) do
    %{conv | status: 404, resp_body: "No #{path} here"}
  end

  def handle_file({:ok, content}, conv) do
    %{conv | status: 200, resp_body: content}
  end

  def handle_file({:error, :enoent}, conv) do
    %{conv | status: 404, resp_body: "File not found"}
  end

  def handle_file({:error, reason}, conv) do
    %{conv | status: 500, resp_body: "File Error: #{reason}"}
  end

  def format_response(conv) do
    # TODO: Use values in the map to create an HTTP response string:
    """
    HTTP/1.1 #{conv.status} #{status_reason(conv.status)}
    Content-Type: text/html
    Content-Length: #{byte_size(conv.resp_body)}

    #{conv.resp_body}
    """
  end

  defp status_reason(code) do
    %{
      200 => "OK",
      201 => "Created",
      401 => "Unauthorized",
      403 => "Forbidden",
      404 => "Not Found",
      500 => "Internal Server Error"
    }[code]
  end
end

request = """
GET /wildthings HTTP/1.1
Host: example.com
User-Agent: ExampleBrowser/1.0
Accept: */*

"""

response = Servy.Handler.handle(request)

IO.puts(response)

request = """
GET /bears HTTP/1.1
Host: example.com
User-Agent: ExampleBrowser/1.0
Accept: */*

"""

response = Servy.Handler.handle(request)

IO.puts(response)

request = """
GET /bigfoot HTTP/1.1
Host: example.com
User-Agent: ExampleBrowser/1.0
Accept: */*

"""

response = Servy.Handler.handle(request)

IO.puts(response)

request = """
GET /bears/1 HTTP/1.1
Host: example.com
User-Agent: ExampleBrowser/1.0
Accept: */*

"""

response = Servy.Handler.handle(request)

IO.puts(response)

request = """
GET /wildlife HTTP/1.1
Host: example.com
User-Agent: ExampleBrowser/1.0
Accept: */*

"""

response = Servy.Handler.handle(request)

IO.puts(response)

request = """
GET /bears?id=1 HTTP/1.1
Host: example.com
User-Agent: ExampleBrowser/1.0
Accept: */*

"""

response = Servy.Handler.handle(request)

IO.puts(response)

request = """
GET /about HTTP/1.1
Host: example.com
User-Agent: ExampleBrowser/1.0
Accept: */*

"""

response = Servy.Handler.handle(request)

IO.puts(response)

request = """
GET /bears/new HTTP/1.1
Host: example.com
User-Agent: ExampleBrowser/1.0
Accept: */*

"""

response = Servy.Handler.handle(request)

IO.puts(response)

However, when I try to see the generated documentation as an exercise, I get an error:

iex h command prompt1243×642 29.3 KB