def defaultModel(t, alpha=3.0, beta=None):
  """Convert recall probability prior's raw parameters into a model object. 🍗

  `t` is your guess as to the half-life of any given fact, in units that you
  must be consistent with throughout your use of Ebisu.

  `alpha` and `beta` are the parameters of the Beta distribution that describe
  your beliefs about the recall probability of a fact `t` time units after that
  fact has been studied/reviewed/quizzed. If they are the same, `t` is a true
  half-life, and this is a recommended way to create a default model for all
  newly-learned facts. If `beta` is omitted, it is taken to be the same as
  `alpha`.
  """
  return (alpha, beta or alpha, t)