Fix bug where format property was not correct for all formats.

Author: hameerabbasi

sparse/numba_backend/_compressed/compressed.py

@@ -259,32 +259,6 @@ def nnz(self):
         """
         return self.data.shape[0]
 
-    @property
-    def format(self):
-        """
-        The storage format of this array.
-
-        Returns
-        -------
-        str
-            The storage format of this array.
-
-        See Also
-        -------
-        [`scipy.sparse.dok_matrix.format`][] : The Scipy equivalent property.
-
-        Examples
-        -------
-        >>> import sparse
-        >>> s = sparse.random((5, 5), density=0.2, format="dok")
-        >>> s.format
-        'dok'
-        >>> t = sparse.random((5, 5), density=0.2, format="coo")
-        >>> t.format
-        'coo'
-        """
-        return "gcxs"
-
     @property
     def nbytes(self):
         """

sparse/numba_backend/_coo/core.py

@@ -601,29 +601,6 @@ def nnz(self):
         """
         return self.coords.shape[1]
 
-    @property
-    def format(self):
-        """
-        The storage format of this array.
-        Returns
-        -------
-        str
-            The storage format of this array.
-        See Also
-        --------
-        [`scipy.sparse.dok_matrix.format`][] : The Scipy equivalent property.
-        Examples
-        -------
-        >>> import sparse
-        >>> s = sparse.random((5, 5), density=0.2, format="dok")
-        >>> s.format
-        'dok'
-        >>> t = sparse.random((5, 5), density=0.2, format="coo")
-        >>> t.format
-        'coo'
-        """
-        return "coo"
-
     @property
     def nbytes(self):
         """

sparse/numba_backend/_dok.py

@@ -272,29 +272,6 @@ def nnz(self):
         """
         return len(self.data)
 
-    @property
-    def format(self):
-        """
-        The storage format of this array.
-        Returns
-        -------
-        str
-            The storage format of this array.
-        See Also
-        -------
-        [`scipy.sparse.dok_matrix.format`][] : The Scipy equivalent property.
-        Examples
-        -------
-        >>> import sparse
-        >>> s = sparse.random((5, 5), density=0.2, format="dok")
-        >>> s.format
-        'dok'
-        >>> t = sparse.random((5, 5), density=0.2, format="coo")
-        >>> t.format
-        'coo'
-        """
-        return "dok"
-
     @property
     def nbytes(self):
         """

sparse/numba_backend/_sparse_array.py

@@ -145,6 +145,34 @@ def size(self):
         # returns a float64 for an empty shape.
         return reduce(operator.mul, self.shape, 1)
 
+    @property
+    def format(self):
+        """
+        The storage format of this array.
+
+        Returns
+        -------
+        str
+            The storage format of this array.
+
+        See Also
+        -------
+        [`scipy.sparse.coo_matrix.format`][] : The Scipy equivalent property.
+        [`scipy.sparse.csr_matrix.format`][] : The Scipy equivalent property.
+        [`scipy.sparse.dok_matrix.format`][] : The Scipy equivalent property.
+
+        Examples
+        -------
+        >>> import sparse
+        >>> s = sparse.random((5, 5), density=0.2, format="dok")
+        >>> s.format
+        'dok'
+        >>> t = sparse.random((5, 5), density=0.2, format="coo")
+        >>> t.format
+        'coo'
+        """
+        return type(self).__name__.lower()
+
     @property
     def density(self):
         """