static @Nullable PsiExpression getDeepQualifier(PsiMethodCallExpression firstCall) {
    PsiExpression firstQualifier = firstCall;
    while (firstQualifier instanceof PsiMethodCallExpression) {
      firstQualifier = ((PsiMethodCallExpression)firstQualifier).getMethodExpression().getQualifierExpression();
    }
    return firstQualifier;
  }
static @Nullable PsiExpression getDeepQualifier(PsiMethodCallExpression firstCall)