@Nullable
  private PsiElement resolvePercentString() {
    final PyBinaryExpression binaryExpression = PsiTreeUtil.getParentOfType(getElement(), PyBinaryExpression.class);
    if (binaryExpression != null) {
      final PyExpression rightExpression = binaryExpression.getRightExpression();
      if (rightExpression == null) {
        return null;
      }
      boolean isKeyWordSubstitution = myChunk.getMappingKey() != null;
      return isKeyWordSubstitution ? resolveKeywordPercent(rightExpression, myChunk.getMappingKey()) : resolvePositionalPercent(rightExpression);
    }
    return null;
  }
@Nullable
  private PsiElement resolvePercentString()