The babel.support modules contains a number of classes and functions that can help with integrating Babel, and internationalization in general, into your application or framework. The code in this module is not used by Babel itself, but instead is provided to address common requirements of applications that should handle internationalization.
One such requirement is lazy evaluation of translations. Many web-based applications define some localizable message at the module level, or in general at some level where the locale of the remote user is not yet known. For such cases, web frameworks generally provide a "lazy" variant of the gettext functions, which basically translates the message not when the gettext function is invoked, but when the string is accessed in some manner.
Many web-based applications are composed of a variety of different components (possibly using some kind of plugin system), and some of those components may provide their own message catalogs that need to be integrated into the larger system.
To support this usage pattern, Babel provides a Translations class that is derived from the GNUTranslations class in the gettext module. This class adds a merge() method that takes another Translations instance, and merges the content of the latter into the main catalog: