Why can't I explicitly call __bool__() on sequence type?

[buran]

I come from Java background where every class implicitly inherits from object class. I was under the assumption it is the same with python.

Actually, you are right - everything inherits from object, at least in python3 (in python2 there were old-style or classical class and new-style class).

You can see with isinstance

>>> type(type)
<class 'type'>
>>> isinstance(type, object)
True
>>> isinstance(str, object)
True
>>> isinstance(type, type)
True
>>> isinstance(str, type)
True
>>> type.__bases__
(<class 'object'>,)
>>> str.__bases__
(<class 'object'>,)