docstr: ...Test gfb astype method
          
docstr_tok: ["...","Test","gfb","astype","method"]
code: def test_gfb_dtype_can_change(self):
      """...Test gfb astype method"""
  
      def create_solver():
          return GFB(max_iter=100, verbose=False, step=0.1)
  
      self._test_solver_astype_consistency(create_solver)
  
file_path: tick/tick/solver/tests/gfb_test.py
imports: import unittest
  import numpy
  from tick.prox import ProxElasticNet, ProxL2Sq, ProxL1
  from tick.solver import GFB, AGD
  from tick.solver.tests import TestSolver
label_desc: Use image node_id 2 for calling the GDBTest obj's underlying member method code with example usage: obj.test_gfb_dtype_can_change() and returns: GFB