@Override
    protected void read() {
        assert children != null;
        if (!children.hasNext()) {
            throw new RuntimeException(
                    "Called SequenceContext.read() too many times!");
        }
        currentChild = children.next();
    }
Create an iterator over the children. May be constructed with a null
JsonArray if we only use it for writing.
thrift/thrift0.13/src/main/java/com/linecorp/armeria/common/thrift/text/SequenceContext.java