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

class ImageOptim
  # Helper methods to manipulate Hash, mainly used in config
  module HashHelpers
    class << self
      # Returns a new hash with all keys of
    
      def deep_merge(hash_a, hash_b)
        hash_a.merge(hash_b) do |_key, value_a, value_b|
          if value_a.is_a?(Hash) && value_b.is_a?(Hash)
            deep_merge(value_a, value_b)
          else
            value_b
          end
        end