def tomatrix(self):
        if self.rank() != 2:
            raise ValueError('Dimensions must be of size of 2')

        mat_sparse = {}
        for key, value in self._sparse_array.items():
            mat_sparse[self._get_tuple_index(key)] = value

        return SparseMatrix(self.shape[0], self.shape[1], mat_sparse)
Converts MutableDenseNDimArray to Matrix. Can convert only 2-dim array, else will raise error.
dataset/ETHPy150Open sympy/sympy/sympy/tensor/array/sparse_ndim_array.py/SparseNDimArray.tomatrix