def load_imports
      while fn = @pending_imports.shift
        next if @imported.member?(fn)
        if fn_task = lookup(fn)
          fn_task.invoke
        end
        ext = File.extname(fn)
        loader = @loaders[ext] || @default_loader
        loader.load(fn)
        @imported << fn
      end
    end
def load_imports
      while fn = @pending_imports.shift
        next if @imported.member?(fn)
        if fn_task = lookup(fn)
          fn_task.invoke
        end
        ext = File.extname(fn)
        loader = @loaders[ext] || @default_loader
        loader.load(fn)
        @imported << fn
      end
    end
Load the pending list of imported files.