You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: model.rb
    path of file: ./repos/pg_ltree/lib/pg_ltree
    
    the code of the file until where you have to start completion: module PgLtree
  module Model
    extend ActiveSupport::Concern

    class_methods do
      def ltree_path_column
        ltree_option_
    
      def leaves
        subquery = unscoped.select("#{table_name}.#{ltree_path_column}")
          .from("#{table_name} AS subquery")
          .where("#{table_name}.#{ltree_path_column} <> subquery.#{ltree_path_column}")
          .where("#{table_name}.#{ltree_path_column} @> subquery.#{ltree_path_column}")

        where.not ltree_path_column => subquery
      end