def j_sparse_vector_wrapper_to_scipy_spmatrix(j_obj: JavaObject):
"""
Convert a Java object of `SparseVectorWrapper` to a scipy sparse matrix whose number of rows is 1.
`j_obj.getSize()` must return a positive number.
NOTE:
- To access i-th element, use `A[0, i]` rather than `A[i]`.
- To convert the sparse matrix to a numpy.ndarray, use `A.todense()`.
- For other usages, please refer to scipy documents.
TODO: find a better type to represent `SparseVector` in Python side.
:param j_obj: a Java object of `SparseVectorWrapper`
:return: a scipy sparse matrix
"""
indices = np.frombuffer(j_obj.getIndicesBytes(), dtype="<i4")
values = np.frombuffer(j_obj.getValuesBytes(), dtype="<f8")
size = j_obj.getSize()
indptr = np.array([0, indices.shape[0]], dtype=np.int32)
return csr_matrix((values, indices, indptr),
shape=(1, size),
dtype=np.float64).todok()
