class_docstr: Abstract class of solver.
class_docstr_tok: ["Abstract","class","of","solver","."]
docstr: Get the model function.
docstr_tok: ["Get","the","model","function","."]
code: def model_fn(self):
      """Get the model function."""
      raise NotImplementedError()
  
imports: import abc
  import math
  import delta.compat
  import tensorflow_addons
  from absl import logging
  from delta import utils
  from delta.utils import optimizer
  from delta.utils.register import registers
label_desc: Use image node_id 3 for calling the ABCSolver obj's underlying member method code with example usage: obj.model_fn() without return types