private static String getSeparator(PyStringLiteralExpression leftExpression) {
    String separator = ""; // detect nontrivial whitespace around the "%"
    Pair<String, PsiElement> crop = collectWhitespace(leftExpression);
    String maybeSeparator = crop.getFirst();
    if (maybeSeparator != null && !maybeSeparator.isEmpty() && !" ".equals(maybeSeparator))
      separator = maybeSeparator;
    else { // after "%"
      crop = collectWhitespace(crop.getSecond());
      maybeSeparator = crop.getFirst();
      if (maybeSeparator != null && !maybeSeparator.isEmpty() && !" ".equals(maybeSeparator))
        separator = maybeSeparator;
    }
    return separator;
  }
private static String getSeparator(PyStringLiteralExpression leftExpression)