def merged_set_or_false(set1, set2):
  if **magic**:
    return merged_set
  else:
    return False

>>> list_of_sets = [(1,2,3,4),(2,3,4,5),(6,7,8,9)]
>>> len(list_of_sets)
3
>>> new_list = merge_until_possible(list_of_sets)
>>> new_list
[(1,2,3,4,5),(6,7,8,9)]
>>> len(new_list)
2