code: def init_group_category_regex(category_groups, category_regex_args):
      
      category_regex = []
      authorized_empty_regex = 1
      if len(category_regex_args) and len(category_groups) != len(category_regex_args):
          printError('Error: you must provide as many regex as category groups.')
          return None
      for regex in category_regex_args:
          if len(regex) < 1:
              if authorized_empty_regex > 0:
                  category_regex.append(None)
                  authorized_empty_regex -= 1
              else:
                  printError('Error: you cannot have more than one empty regex to automatically assign groups to users.')
                  return None
          else:
              category_regex.append(re.compile(regex))
      return category_regex
docs: Initialize and compile regular expression for category groups
  
      :param category_regex_args:         List of string regex
  
      :return:                            List of compiled regex