In this chapter, we got our feet wet by creating custom operators. It is preferable to use ObservableTransformer and FlowableTransformer to compose a new operator from the existing ones, and even with that, you need to be cautious when introducing stateful resources that cause undesirable side effects.
When all else fails, you can create your own ObservableOperator or FlowableOperator and create an operator at a low level that intercepts and relays each emission and event. This can be tricky and you should exhaust all other options, but with careful study and testing, creating operators can be a valuable advanced skill to have. Just be careful to not reinvent the wheel and seek guidance from the Rx community as you start dabbling in custom operators.
If you truly are interested in implementing your own operators (at a low level, not with transformers), definitely study...
