Possible redundant assertion `issubclass(type(a), type(a))`

[rc4typecheck]

Since a class is considered a subclass of itself, the expression issubclass(type(a), type(a)) is always True. Therefore, the following three assert statements in /pandas/tests/dtypes/test_dtypes.py seem redundant and meaningless to me:

class TestDatetimeTZDtype(Base):
    def test_subclass(self):
        assert issubclass(type(a), type(a))

class TestPeriodDtype(Base):
    def test_subclass(self):
        assert issubclass(type(a), type(a))

class TestIntervalDtype(Base):
    def test_subclass(self):
        assert issubclass(type(a), type(a))

If there is some special purpose behind the assertion, could you please confirm? Thanks.

[rustamali9183]

Hi, I’m a new contributor and would like to work on this.
Plan: remove the redundant issubclass(type(a), type(a)) assertions in test_dtypes.py (or replace them with a more meaningful subclass check if you prefer).
Please let me know if this is acceptable and if you have any preference for what the test should assert instead.

[rhshadrach]

Since a class is considered a subclass of itself, the expression issubclass(type(a), type(a)) is always True.

This isn't exactly true because of metaclasses and __subclasscheck__. I'm only seeing that defined on OffsetMeta.

+1 on removing the assert.

[rc4typecheck]

Hi, @rhshadrach . Thanks for pointing out the mechanism of metaclasses and __subclasscheck__!

And thanks to @rustamali9183 for removing the redundant assertions!