docstr: add a function interface and axis
docstr_tok: ["add","a","function","interface","and","axis"]
code: def __init_func(self):
      """add a function interface and axis"""
      from mystic.math.interpolate import _to_function
  
      self.__func__ = _to_function(self.__model__, ndim=self.nx)
      if hasattr(self.__func__, "__axis__"):
          self.__axis__ = self.__func__.__axis__
      else:
          if self.ny is None:  # i.e. multivalued=False
              self.__axis__ = None
          else:
  
              def build_it(axis):
                  func = self.__func__
                  return lambda *x, **kwds: func(*x, axis=axis, **kwds)
  
              self.__axis__ = [build_it(i) for i in range(self.ny)]
          self.__func__.__axis__ = self.__axis__
      return
  
label_desc: Use image node_id 4 for calling the OUQModel obj's underlying member method code with example usage: obj.__init_func() and returns: function