def generate_diff_for_language(current_language, target_language)
    current_langmap = langmap[current_language]
    target_langmap = langmap[target_language]
    diffmap_key = [current_language, target_language]
    diffmap[diffmap_key] = current_langmap - target_langmap
  end
def generate_diff_for_language(current_language, target_language)
    current_langmap = langmap[current_language]
    target_langmap = langmap[target_language]
    diffmap_key = [current_language, target_language]
    diffmap[diffmap_key] = current_langmap - target_langmap
  end
a diffmap shows what is missing between two languages
 the key is a two-element array, the first element is the current language
 and the second element is the target language

 for example
 diffmap: {[:en, :fr] => [[:obj3], ...]}

 means that fr was examined against en, where en had an entry for obj3 that fr didn't