class_docstr: Chebyshev polynomial models and functions,
  including specific methods for Tn(z) n=2,4,6,8,16, Equation (27-33) of [2]
  
  NOTE: default is T8(z)
code: def __call__(self, *args, **kwds):
      return self.forward(*args, **kwds)
  
imports: from .abstract_model import AbstractModel
  from numpy import sum
  from numpy import asarray
  from mystic.math import polyeval, poly1d
  from mystic.models._model_helper import chebyshev2coeffs, chebyshev4coeffs, chebyshev6coeffs, chebyshev8coeffs, chebyshev16coeffs
label_desc: Use image node_id 2 for calling the Chebyshev obj's underlying member method code with example usage: obj.__call__() and returns: self