replace backend methods with `__getattr__`?

[amirreza8002]

as noted in #25 (comment)
most of the methods in backend classes are simple doing self.client.method_name(),
so we should investigate if it's appropriate to remove these methods and handle all of it with a __getattr__ method, tho not all methods can be handled like this.

it should be noted that doing this requires handling omit_exception decorator as well, since that's applied on backend methods.

one way to handle it would be t just move the decorator to client level, but some methods such as get resist this idea, which would lead to having the decorator in some client methods and some backend methods.

another way would be to to call the decorator inside __getattr__, i have not tested this.