addOp method
Implementation
@visibleForTesting
void addOp(String op, String key, dynamic value) {
assert([
OP_SET,
OP_SET_ONCE,
OP_ADD,
OP_APPEND,
OP_UNSET,
OP_PREPEND,
OP_PREINSERT,
OP_POSTINSERT,
OP_REMOVE,
OP_CLEAR_ALL,
].contains(op));
_opMap(op)[key] = value;
}