MNT: Move constructors to a direct style (#773)

Author: mtsokol

sparse/mlir_backend/_common.py

@@ -1,5 +1,7 @@
 import abc
+import ctypes
 import functools
+import weakref
 
 from mlir import ir
 
@@ -12,3 +14,23 @@ def get_mlir_type(cls) -> ir.Type: ...
 
 def fn_cache(f, maxsize: int | None = None):
     return functools.wraps(f)(functools.lru_cache(maxsize=maxsize)(f))
+
+
+def _hold_self_ref_in_ret(fn):
+    @functools.wraps(fn)
+    def wrapped(self, *a, **kw):
+        ret = fn(self, *a, **kw)
+        _take_owneship(ret, self)
+        return ret
+
+    return wrapped
+
+
+def _take_owneship(owner, obj):
+    ptr = ctypes.py_object(obj)
+    ctypes.pythonapi.Py_IncRef(ptr)
+
+    def finalizer(ptr):
+        ctypes.pythonapi.Py_DecRef(ptr)
+
+    weakref.finalize(owner, finalizer, ptr)