Generate a lil_matrix of dimensions (r,c) with the k-th diagonal set to 1.
r,c : int
row and column-dimensions of the output.
k : int
diagonal offset. In the output matrix, out[m,m+k] == 1 for all m.
dtype : dtype
data-type of the output array.
scipy.sparse.kronsum
scipy.sparse.lil_diags