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This is as designed. The only method needed for something to qualify as an Iterable is __iter__, thus this is the only method defined on the ABC. If you want your Iterable to be usable in a boolean test, add the __bool__ method to your concrete class.
In fact, you will note that no ABCs define __bool__.
Likewise __len__ is not part of being an Iterator, and in fact in the general case Iterators do not have a len (a given Iterator might be infinite, or it might not be practical to calculate the len).