Ruby Impressionist gem error

Question

i wan to use this gem im my proyect on ruby on rails 4.0 but when i do all instructions of this gem in my proyect i get this error:

    NoMethodError in ProductsController#show 
undefined method `impressionist' for #<ProductsController:0x4d30400>

Image of the error

I just want to count how many times you see every post that exists on my website

this is my controller:

class ProductsController < ApplicationController
  before_action :set_product, only: [:show, :edit, :update, :destroy]

  # GET /products
  # GET /products.json
  def index
    @products = Product.all
  end

  # GET /products/1
  # GET /products/1.json
  def show
    @product = Product.find(params[:id])
    impressionist(@product)
  end

  # GET /products/new
  def new
    @product = Product.new
  end

  # GET /products/1/edit
  def edit
  end

  # POST /products
  # POST /products.json
  def create
    @product = Product.new(product_params)

    respond_to do |format|
      if @product.save
        format.html { redirect_to @product, notice: 'Product was successfully created.' }
        format.json { render :show, status: :created, location: @product }
      else
        format.html { render :new }
        format.json { render json: @product.errors, status: :unprocessable_entity }
      end
    end
  end

  # PATCH/PUT /products/1
  # PATCH/PUT /products/1.json
  def update
    respond_to do |format|
      if @product.update(product_params)
        format.html { redirect_to @product, notice: 'Product was successfully updated.' }
        format.json { render :show, status: :ok, location: @product }
      else
        format.html { render :edit }
        format.json { render json: @product.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /products/1
  # DELETE /products/1.json
  def destroy
    @product.destroy
    respond_to do |format|
      format.html { redirect_to products_url, notice: 'Product was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_product
      @product = Product.find(params[:id])
    end

    # Never trust parameters from the scary internet, only allow the white list through.
    def product_params
      params.require(:product).permit(:nombre, :tipo)
    end
end

My model:

class Product < ApplicationRecord
  include Impressionist::IsImpressionable
  is_impressionable
end

index.html.erb:

<p id="notice"><%= notice %></p>

<h1>Products</h1>

<table>
  <thead>
    <tr>
      <th>Nombre</th>
      <th>Tipo</th>
      <th>Views</th>
      <th colspan="3"></th>
    </tr>
  </thead>

  <tbody>
    <% @products.each do |product| %>
      <tr>
        <td><%= product.nombre %></td>
        <td><%= product.tipo %></td>
        td><%= product.impressionist_count %></td>
        <td><%= link_to 'Show', product %></td>
        <td><%= link_to 'Edit', edit_product_path(product) %></td>
        <td><%= link_to 'Destroy', product, method: :delete, data: { confirm: 'Are you sure?' } %></td>
      </tr>
    <% end %>
  </tbody>
</table>

<br>

<%= link_to 'New Product', new_product_path %>

show.html.erb:

<p id="notice"><%= notice %></p>

<p>
  <strong>Nombre:</strong>
  <%= @product.nombre %>
</p>

<p>
  <strong>Tipo:</strong>
  <%= @product.tipo %>
</p>

<%= link_to 'Edit', edit_product_path(@product) %> |
<%= link_to 'Back', products_path %>

db migration:

class CreateImpressionsTable < ActiveRecord::Migration[5.1]
  def self.up
    create_table :impressions, :force => true do |t|
      t.string :impressionable_type
      t.integer :impressionable_id
      t.integer :user_id
      t.string :controller_name
      t.string :action_name
      t.string :view_name
      t.string :request_hash
      t.string :ip_address
      t.string :session_hash
      t.text :message
      t.text :referrer
      t.text :params
      t.timestamps
    end
    add_index :impressions, [:impressionable_type, :message, :impressionable_id], :name => "impressionable_type_message_index", :unique => false, :length => {:message => 255 }
    add_index :impressions, [:impressionable_type, :impressionable_id, :request_hash], :name => "poly_request_index", :unique => false
    add_index :impressions, [:impressionable_type, :impressionable_id, :ip_address], :name => "poly_ip_index", :unique => false
    add_index :impressions, [:impressionable_type, :impressionable_id, :session_hash], :name => "poly_session_index", :unique => false
    add_index :impressions, [:controller_name,:action_name,:request_hash], :name => "controlleraction_request_index", :unique => false
    add_index :impressions, [:controller_name,:action_name,:ip_address], :name => "controlleraction_ip_index", :unique => false
    add_index :impressions, [:controller_name,:action_name,:session_hash], :name => "controlleraction_session_index", :unique => false
    add_index :impressions, [:impressionable_type, :impressionable_id, :params], :name => "poly_params_request_index", :unique => false
    add_index :impressions, :user_id
  end

  def self.down
    drop_table :impressions
  end
end

Obviously i installed the gem: gem 'impressionist' in my gemfile, run bundle install, generate the impressionist and all And all the steps indicated in manual installation