public VirtualFilePattern withExtension(final @NonNls @NotNull String extension) {
    return with(new PatternCondition<VirtualFile>("withExtension") {
      @Override
      public boolean accepts(final @NotNull VirtualFile virtualFile, final ProcessingContext context) {
        return extension.equals(virtualFile.getExtension());
      }
    });
  }
public VirtualFilePattern withExtension(final @NonNls @NotNull String extension)