code: def _get_century_code(year):
          
          if 2000 <= year < 3000:
              separator = 'A'
          elif 1900 <= year < 2000:
              separator = '-'
          elif 1800 <= year < 1900:
              separator = '+'
          else:
              raise ValueError('Finnish SSN do not support people born before the year 1800 or after the year 2999')
          return separator
docs: Returns the century code for a given year