message: print -> assert
diff: @@ -536,13 +536,11 @@ cdef class SimplexTree:
  :note: lower_star_persistence_generators requires that `persistence()` be called first.
  """
  - if self.pcohptr != NULL:
  + assert self.pcohptr != NULL, "lower_star_persistence_generators() requires that persistence() be called first."
  gen = self.pcohptr.lower_star_generators()
  normal = [np_array(d).reshape(-1,2) for d in gen.first]
  infinite = [np_array(d) for d in gen.second]
  return (normal, infinite)
  - else:
  - print("lower_star_persistence_generators() requires that persistence() be called first.")
  def flag_persistence_generators(self):
  """Assuming this is a flag complex, this function returns the persistence pairs,
  @@ -556,7 +554,7 @@ cdef class SimplexTree:
  :note: flag_persistence_generators requires that `persistence()` be called first.
  """
  - if self.pcohptr != NULL:
  + assert self.pcohptr != NULL, "flag_persistence_generators() requires that persistence() be called first."
  gen = self.pcohptr.flag_generators()
  if len(gen.first) == 0:
  normal0 = numpy.empty((0,3))
  @@ -572,7 +570,4 @@ cdef class SimplexTree:
  l = iter(gen.second)
  infinite0 = np_array(next(l))
  infinites = [np_array(d).reshape(-1,2) for d in l]
  -
  return (normal0, normals, infinite0, infinites)
  - else:
  - print("flag_persistence_generators() requires that persistence() be called first.")
  