@Nullable
  private static ChainCompletionContext extractContextFromAssignment(PsiAssignmentExpression assignmentExpression,
                                                                     CompletionParameters parameters) {
    PsiExpression lExpr = assignmentExpression.getLExpression();
    if (!(lExpr instanceof PsiReferenceExpression)) return null;
    PsiElement resolved = ((PsiReferenceExpression)lExpr).resolve();
    return resolved instanceof PsiVariable
           ? ChainCompletionContext.createContext(((PsiVariable)resolved).getType(), assignmentExpression, suggestIterators(parameters))
           : null;
  }
@Nullable
  private static ChainCompletionContext extractContextFromAssignment(PsiAssignmentExpression assignmentExpression,
                                                                     CompletionParameters parameters)