Revise contains logic: interval contains itself or equivalent interval

Author: rlskoeser

src/undate/interval.py

@@ -125,14 +125,12 @@ def duration(self) -> Timedelta:
 
     def __contains__(self, other: object) -> bool:
         """Determine if another interval or date falls within this
-        interval."""
-        # support comparison with another interval
+        interval.  Supports comparison with :class:`UndateInterval`
+        or anything that can be converted with :meth:`Undate.to_undate`."""
+        # support comparison with another interval or anything
+        # that can be converted to an Undate
         if isinstance(other, UndateInterval):
-            # if two intervals are strictly equal, don't consider
-            # either one as containing the other
-            if self == other:
-                return False
-            # otherwise compare based on earliest/latest bounds
+            # compare based on earliest/latest bounds
             other_earliest = other.earliest
             other_latest = other.latest
         else:

tests/test_interval.py

@@ -186,9 +186,9 @@ def test_contains(self):
         century11th = UndateInterval(Undate(1001), Undate(1100))
         century20th = UndateInterval(Undate(1901), Undate(2000))
         decade1990s = UndateInterval(Undate(1990), Undate(1999))
-        # an interval doesn't contain itself
+        # an interval DOES contain itself
         for interval in [century11th, century20th, decade1990s]:
-            assert interval not in interval
+            assert interval in interval
 
         # checking if an interval is within another interval
         assert decade1990s in century20th
@@ -228,4 +228,6 @@ def test_contains(self):
         # fully open interval - is this even meaningful?
         whenever = UndateInterval(None, None)
         assert decade1990s in whenever
-        assert whenever not in whenever
+        # NOTE: an interval contains itself or an equivalent interval,
+        # but that may not make sense for open intervals...
+        assert whenever in whenever