allow empty storage

torch_sparse/storage.py

@@ -155,6 +155,19 @@ class SparseStorage(object):
                 self._csr2csc = None
                 self._csc2csr = None
 
+    @classmethod
+    def empty(self):
+        self = SparseStorage.__new__(SparseStorage)
+        self._row = None
+        self._rowptr = None
+        self._value = None
+        self._rowcount = None
+        self._colptr = None
+        self._colcount = None
+        self._csr2csc = None
+        self._csc2csr = None
+        return self
+
     def has_row(self) -> bool:
         return self._row is not None
 
@@ -605,19 +618,3 @@ def is_shared(self) -> bool:
 
 SparseStorage.share_memory_ = share_memory_
 SparseStorage.is_shared = is_shared
-
-
-def __new__(cls, *args, **kwargs):
-    instance = super(SparseStorage, cls).__new__(cls, *args, **kwargs)
-    instance._row = None
-    instance._rowptr = None
-    instance._value = None
-    instance._rowcount = None
-    instance._colptr = None
-    instance._colcount = None
-    instance._csr2csc = None
-    instance._csc2csr = None
-    return instance
-
-
-SparseStorage.__new__ = __new__