Some Math background
The normalized Laplacian of the graph G is the matrix L(G) defined as followed:
L(G) (u, v) = -(du+dv)-1/2 if u and v are adj.
The normalized Laplacian spectrum (nls) is the set of eigenvalues of L(G), i.e., all values ? such that
L(G)*u = ?*u for some u?Rn, u?0
Multiplicity of eigenvalue a equals to how many of the n eigenvalues are a