class_docstr: Base class for mystic models
  
  The 'evaluate' and 'ForwardFactory' methods must be overwritten, thus providing
  a standard interface for generating a forward model factory and evaluating a
  forward model.  Additionally, two common ways to generate a cost function are
  built into the model.  For "standard models", the cost function generator will
  work with no modifications.
  
  See `mystic.models.poly` for a few basic examples.
      
docstr: generates a forward model instance from a list of coefficients
docstr_tok: ["generates","a","forward","model","instance","from","a","list","of","coefficients"]
code: def ForwardFactory(self, coeffs):
      """generates a forward model instance from a list of coefficients"""
      raise NotImplementedError("overwrite for each derived class")
  
file_path: mystic/mystic/models/abstract_model.py
imports: from numpy import sum
  from mystic.forward_model import CostFactory
label_desc: Use image node_id 3 for calling the AbstractModel obj's underlying member method code with example usage: obj.ForwardFactory(coeffs) without return types