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: boxcars.rb
    path of file: ./repos/boxcars/lib
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

require 'logger'

# Boxcars is a framework for running a series of tools to get an answer to a question.
module Boxcars
  # Error class for all Boxcars errors.
  class Error < StandardError; end

  # Error class for all Boxcars configuration errors.
  class ConfigurationError < Error; end

    
    def key_lookup(key, kwargs)
      val = if kwargs.key?(key) && !kwargs[key].nil?
              # override with kwargs if present
              kwargs[key]
            elsif (provided_val = instance_variable_get("@#{key}"))
              # use saved value if present. Set using Boxcars.configuration.the_key = "abcde"
              provided_val
            else
              # otherwise, dig out of the environment
              env_val = ENV.fetch(key.to_s.upcase, nil)
              env_val
            end