code: def DefaultEnvironment(*args, **kw):
      
      global _default_env
      if not _default_env:
          import SCons.Util
          _default_env = SCons.Environment.Environment(*args, **kw)
          if SCons.Util.md5:
              _default_env.Decider('MD5')
          else:
              _default_env.Decider('timestamp-match')
          global DefaultEnvironment
          DefaultEnvironment = _fetch_DefaultEnvironment
          _default_env._CacheDir_path = None
      return _default_env
docs: Initial public entry point for creating the default construction
      Environment.
  
      After creating the environment, we overwrite our name
      (DefaultEnvironment) with the _fetch_DefaultEnvironment() function,
      which more efficiently returns the initialized default construction
      environment without checking for its existence.
  
      (This function still exists with its _default_check because someone
      else (*cough* Script/__init__.py *cough*) may keep a reference
      to this function.  So we can't use the fully functional idiom of
      having the name originally be a something that *only* creates the
      construction environment and then overwrites the name.)