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)
docstr: The costfunction for order-n Chebyshev fitting.
  M evaluation points between [-1, 1], and two end points
docstr_tok: ["The","costfunction","for","order-n","Chebyshev","fitting",".","M","evaluation","points","between","[","-1",",","1","]",",","and","two","end","points"]
code: def cost(self, trial, M=61):
      """The costfunction for order-n Chebyshev fitting.
      M evaluation points between [-1, 1], and two end points"""  # % (len(self.coeffs)-1)
      # XXX: throw error when len(trial) != len(self.coeffs) ?
      myCost = chebyshevcostfactory(self.coeffs)
      return myCost(trial, M)
  
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 7 for calling the Chebyshev obj's underlying member method code with example usage: obj.cost(trial, M) and returns: myCost