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

[quazirfan]

In this code, if foo: python will call foo.__bool__() implicitly to get the boolean value of foo. Which is why the following code segments work,

if 't': print("T") 
if [1]: print("T")

But I wanted to check if I can call the __bool__() method myself like the following;

't'.__bool__() # AttributeError: 'str' object has no attribute '__bool__'
[1].__bool__() # AttributeError: 'list' object has no attribute '__bool__'

As you can see it do not work, and in both cases I get AttributeError.

If __bool__() can be called implicitly in a if statement, why can I not call it explicitly?