code: def agerange(self, m, feh=0.0):
          
          ages = np.arange(self.minage, self.maxage, 0.01)
          rs = self.radius(m, ages, feh)
          w = np.where(np.isfinite(rs))[0]
          return ages[w[0]],ages[w[-1]]
docs: For a given mass and feh, returns the min and max allowed ages.