code: def _parse_key_from_substring(substring) -> str:
      '''
      Returns the key in the expected string "N:12.3", where "N" is the
      key, and "12.3" is a floating point value
      '''
      try:
          return substring.split(':')[0]
      except (ValueError, IndexError, TypeError, AttributeError):
          log.exception('Unexpected argument to _parse_key_from_substring:')
          raise ParseError(
              'Unexpected argument to _parse_key_from_substring: {}'.format(
                  substring)f _parse_key_from_substring(substring) -> str:
      '''
      Returns the key in the expected string "N:12.3", where "N" is the
      key, and "12.3" is a floating point value
      '''
      try:
          return substring.split(':')[0]
      except (ValueError, IndexError, TypeError, AttributeError):
          log.exception('Unexpected argument to _parse_key_from_substring:')
          raise ParseError(
              'Unexpected argument to _parse_key_from_substring: {}'.format(
                  substring))
docs: Returns the key in the expected string "N:12.3", where "N" is the
      key, and "12.3" is a floating point value