@Nullable
  public static String getSignature(@NotNull PsiElement element) {
    for(ElementSignatureProvider provider: ElementSignatureProvider.EP_NAME.getExtensionList()) {
      String signature = provider.getSignature(element);
      if (signature != null) return signature;
    }
    return GENERIC_PROVIDER.getSignature(element);
  }
@Nullable
  public static String getSignature(@NotNull PsiElement element)