private ExpressionFunction readExpression(String name, BufferedReader reader)
                throws IOException, ParseException {
            // First line is expression
            RankingExpression expression = new RankingExpression(name, reader.readLine());
            // Next lines are inputs on the format name\ttensorTypeSpec
            Map<String, TensorType> inputs = new LinkedHashMap<>();
            String line;
            while (null != (line = reader.readLine())) {
                String[] parts = line.split("\t");
                inputs.put(parts[0], TensorType.fromSpec(parts[1]));
            }
            return new ExpressionFunction(name, new ArrayList<>(inputs.keySet()), expression, inputs, Optional.empty());
        }
Adds this expression to the application package, such that it can be read later.

@param name the name of this ranking expression - may have 1-3 parts separated by dot where the first part
            is always the model name
config-model/src/main/java/com/yahoo/vespa/model/ml/ConvertedModel.java