code: def parse_hyphen_range(self, value):
          
          values = value.strip().split('-')
          values = list(map(strip, values))
          if len(values) == 1:
              lower = upper = value.strip()
          elif len(values) == 2:
              lower, upper = values
              if lower == '':
                  # Parse range such as '-3'
                  upper = '-' + upper
                  lower = upper
          else:
              if len(values) > 4:
                  raise IntervalException(
                      'Unknown interval format given.'
                  )
              values_copy = []
              for key, value in enumerate(values):
                  if value != '':
                      try:
                          if values[key - 1] == '':
                              value = '-' + value
                      except IndexError:
                          pass
                      values_copy.append(value)
              lower, upper = values_copy
  
          return [lower, upper], True, True
docs: Parse hyphen ranges such as: 2 - 5, -2 - -1, -3 - 5