private static Map<PyExpression, PyExpression> addSubscriptions(PsiFile file, String operand) {
        Map<PyExpression, PyExpression> additionalExpressions = new HashMap<>();
        Collection<PySubscriptionExpression> subscriptionExpressions = PsiTreeUtil.findChildrenOfType(file, PySubscriptionExpression.class);
        for (PySubscriptionExpression expr : subscriptionExpressions) {
          if (expr.getOperand().getText().equals(operand)) {
            PsiElement parent = expr.getParent();
            if (parent instanceof PyAssignmentStatement) {
              if (expr.equals(((PyAssignmentStatement)parent).getLeftHandSideExpression())) {
                PyExpression key = expr.getIndexExpression();
                if (key != null) {
                  additionalExpressions.put(key, ((PyAssignmentStatement)parent).getAssignedValue());
                }
              }
            }
          }
        }
        return additionalExpressions;
      }
private static Map<PyExpression, PyExpression> addSubscriptions(PsiFile file, String operand)