code: def mirror_sources(self, sourcedir, targetdir=None, recursive=True,
                         excludes=[]):
          
          sources = self.compilable_sources(
              sourcedir,
              absolute=False,
              recursive=recursive,
              excludes=excludes
          )
          maplist = []
  
          for filepath in sources:
              src = filepath
              dst = self.get_destination(src, targetdir=targetdir)
  
              # In absolute mode
              if targetdir:
                  src = os.path.join(sourcedir, src)
  
              maplist.append((src, dst))
  
          return maplist
docs: Mirroring compilable sources filepaths to their targets.
  
          Args:
              sourcedir (str): Directory path to scan.
  
          Keyword Arguments:
              absolute (bool): Returned paths will be absolute using
                  ``sourcedir`` argument (if True), else return relative paths.
              recursive (bool): Switch to enabled recursive finding (if True).
                  Default to True.
              excludes (list): A list of excluding patterns (glob patterns).
                  Patterns are matched against the relative filepath (from its
                  sourcedir).
  
          Returns:
              list: A list of pairs ``(source, target)``. Where ``target`` is the
                  ``source`` path but renamed with ``.css`` extension. Relative
                  directory from source dir is left unchanged but if given,
                  returned paths will be absolute (using ``sourcedir`` for
                  sources and ``targetdir`` for targets).