How to use the @angular/language-service/src/expressions.getExpressionCompletions function in @angular/language-service

ExpressionVisitor.prototype.visitBoundText = function (ast) {
            var expressionPosition = this.position - ast.sourceSpan.start.offset;
            if (utils_1.inSpan(expressionPosition, ast.value.span)) {
                var completions = expressions_1.getExpressionCompletions(this.getExpressionScope(), ast.value, expressionPosition, this.info.template.query);
                if (completions) {
                    this.result = this.symbolsToCompletions(completions);
                }
            }
        };
        ExpressionVisitor.prototype.attributeValueCompletions = function (value, position) {

ExpressionVisitor.prototype.attributeValueCompletions = function (value, position) {
            var symbols = expressions_1.getExpressionCompletions(this.getExpressionScope(), value, position == null ? this.attributeValuePosition : position, this.info.template.query);
            if (symbols) {
                this.result = this.symbolsToCompletions(symbols);
            }
        };
        ExpressionVisitor.prototype.symbolsToCompletions = function (symbols) {