docstr: ...Test saga astype method
          
docstr_tok: ["...","Test","saga","astype","method"]
code: def test_saga_dtype_can_change(self):
      """...Test saga astype method"""
  
      def create_solver():
          return SAGA(
              max_iter=100,
              verbose=False,
              step=0.01,
              seed=TestSolver.sto_seed,
          )
  
      self._test_solver_astype_consistency(create_solver)
  
imports: import unittest
  import numpy
  from scipy import sparse
  from tick.prox import ProxElasticNet
  from tick.solver import SAGA
  from tick.solver.tests import TestSolver
  from tick.solver.build.solver import SAGADouble
  from tick.linear_model import ModelLogReg, SimuLogReg
  from tick.survival import SimuCoxReg, ModelCoxRegPartialLik
  from tick.simulation import weights_sparse_gauss
label_desc: Use image node_id 4 for calling the SAGATest obj's underlying member method code with example usage: obj.test_saga_dtype_can_change() and returns: SAGA