set theoretic methods always return a geometry
Add a note about the set-theoretic methods always returning a geometry and how to treat that in conditions. Ref
@@ -1356,6 +1356,13 @@ Almost every binary predicate method has a counterpart that returns a new
geometric object. In addition, the set-theoretic `boundary` of an object is
available as a read-only attribute.
+.. note::
+
+ These methods will `always` return a geometric object. An intersection of
+ disjoint geometries for example will return an empty `GeometryCollection`,
+ not `None` or `False`. To test for a non-empty result, use the geometry's
+ :ref:`is_empty` property.
+
.. attribute:: object.boundary
Returns a lower dimensional object representing the object's set-theoretic
