ValueError: object dtype is not supported by sparse matrices

[smarie]

In recent scipy (1.9.1) using sparse.dok_matrix does not work anymore with object-typed arrays

..\main.py:524: in fit_selector_model
    model.fit(X)
..\selector.py:100: in fit
    self._maps = maps = sparse.dok_matrix((n, n), dtype=object)
..\..\.nox\tests-3-8\lib\site-packages\scipy\sparse\_dok.py:78: in __init__
    self.dtype = getdtype(dtype, default=float)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

dtype = <class 'object'>, a = None, default = <class 'float'>

    def getdtype(dtype, a=None, default=None):
        """Function used to simplify argument processing. If 'dtype' is not
        specified (is None), returns a.dtype; otherwise returns a np.dtype
        object created from the specified dtype argument. If 'dtype' and 'a'
        are both None, construct a data type out of the 'default' parameter.
        Furthermore, 'dtype' must be in 'allowed' set.
        """
        # TODO is this really what we want?
        if dtype is None:
            try:
                newdtype = a.dtype
            except AttributeError as e:
                if default is not None:
                    newdtype = np.dtype(default)
                else:
                    raise TypeError("could not interpret data type") from e
        else:
            newdtype = np.dtype(dtype)
            if newdtype == np.object_:
>               raise ValueError(
                    "object dtype is not supported by sparse matrices"
                )
E               ValueError: object dtype is not supported by sparse matrices

..\..\.nox\tests-3-8\lib\site-packages\scipy\sparse\_sputils.py:113: ValueError