static @Nullable String getMethodReferenceClassName(PsiMethodReferenceExpression expression) {
    PsiExpression qualifierExpression = expression.getQualifierExpression();
    if (!(qualifierExpression instanceof PsiReferenceExpression)) return null;
    PsiElement refType = ((PsiReference)qualifierExpression).resolve();
    if (!(refType instanceof PsiClass)) return null;
    return ((PsiClass)refType).getQualifiedName();
  }
static @Nullable String getMethodReferenceClassName(PsiMethodReferenceExpression expression)