code: def init_solver(self, L):
      global sp
      import scipy as sp
  
      ilu = sp.sparse.linalg.spilu(self.L1.tocsc())
      n = self.n - 1
      self.M = sp.sparse.linalg.LinearOperator(
          shape=(n, n), matvec=ilu.solve
      )
  
imports: import networkx
label_desc: Use image node_id 1 for calling the CGInverseLaplacian obj's underlying member method code with example usage: obj.init_solver(L) without return types