code: def evaluate_model(coeffs, w, c=None):
      if c is None:
          err = norm(coeffs - w)
      else:
          err = abs(c - coeffs[-1])
          err += norm(coeffs[:-1] - w)
      return err
  
file_path: tick/tick/solver/tests/solver.py
imports: import unittest
  import itertools
  import numpy
  from scipy.linalg import norm
  from scipy.sparse import csr_matrix
  from tick.linear_model import ModelLogReg, ModelPoisReg, ModelLinReg, SimuLinReg, SimuLogReg, SimuPoisReg
  from tick.prox import ProxL2Sq, ProxZero, ProxL1
  from tick.solver import SVRG, AGD, SGD, SDCA, GD, BFGS, AdaGrad
  from tick.simulation import weights_sparse_gauss
label_desc: Use image node_id 8 for calling the TestSolver obj's underlying member method code with example usage: obj.evaluate_model(coeffs, w, c) and returns: err