class_docstr: A generic link function for one-parameter exponential
  family, with call, inverse and deriv methods.
code: def initialize(self, Y):
      return np.asarray(Y).mean() * np.ones(Y.shape)
  
imports: import numpy
  import scipy.stats
label_desc: Use image node_id 1 for calling the Link obj's underlying member method code with example usage: obj.initialize(Y) and returns: unknown