Implement __eq__ and __hash__ for Aggregation objects

Use the matching C++ implementations for OAOO.

python/cudf/cudf/_lib/cpp/aggregation.pxd

@@ -1,4 +1,5 @@
 # Copyright (c) 2020-2024, NVIDIA CORPORATION.
+from libc.stddef cimport size_t
 from libc.stdint cimport int32_t
 from libcpp cimport bool
 from libcpp.memory cimport unique_ptr
@@ -51,6 +52,8 @@ cdef extern from "cudf/aggregation.hpp" namespace "cudf" nogil:
     cdef cppclass aggregation:
         Kind kind
         unique_ptr[aggregation] clone()
+        size_t do_hash() noexcept
+        bool is_equal(const aggregation const) noexcept
 
     cdef cppclass rolling_aggregation(aggregation):
         pass

python/cudf/cudf/_lib/pylibcudf/aggregation.pyx

@@ -77,6 +77,14 @@ cdef class Aggregation:
             "Aggregations should not be constructed directly. Use one of the factories."
         )
 
+    def __eq__(self, other):
+        return type(self) is type(other) and (
+            dereference(self.c_obj).is_equal(dereference((<Aggregation>other).c_obj))
+        )
+
+    def __hash__(self):
+        return dereference(self.c_obj).do_hash()
+
     # TODO: Ideally we would include the return type here, but we need to do so
     # in a way that Sphinx understands (currently have issues due to
     # https://github.com/cython/cython/issues/5609).