namespace consistency for test_dtype.py (#37843)

* namespace consistency for test_dtype.py

* namespace inconsistency fix to test_interval.py

* reverting changes to test_dtype.py

* fix flake8 error

* fix Interval change

* adding back pd.IntervalDtype

Author: reshamas

pandas/tests/arithmetic/test_interval.py

@@ -290,6 +290,6 @@ def test_index_series_compat(self, op, constructor, expected_type, assert_func):
     def test_comparison_operations(self, scalars):
         # GH #28981
         expected = Series([False, False])
-        s = Series([pd.Interval(0, 1), pd.Interval(1, 2)], dtype="interval")
+        s = Series([Interval(0, 1), Interval(1, 2)], dtype="interval")
         result = s == scalars
         tm.assert_series_equal(result, expected)