private void parseArgument(int pendingTextStart) {
            if (parser.peek() == '{') {
                parseBracedArgument(pendingTextStart);
            } else {
                // Output any pending captured text before the output of the expression.
                if (pendingTextStart > -1) {
                    pushOperation(Operation.stringSlice(parser.input(), pendingTextStart, parser.position() - 1));
                }
                pushOperation(parseNormalArgument());
            }
        }
A BlockOperation that repeats a template for each value referenced by the block. Each iteration pushes
a state to the writer that includes key, value, key.first, and key.last context properties. The name
of the context property can be customized in the template.
smithy-utils/src/main/java/software/amazon/smithy/utils/CodeFormatter.java