code: def _deserialize(self, value, attr, obj):
          
          if value is None:
              return None
  
          try:
              return float(value)
          except ValueError:
              parsed = parser.parse(value)
              if parsed.tzinfo:
                  if parsed.utcoffset().total_seconds():
                      raise ValidationError("Timestamps must be defined in UTC")
                  parsed = parsed.replace(tzinfo=None)
              return (parsed - TimestampField.EPOCH).total_seconds()
docs: Deserialize value as a Unix timestamp (in float seconds).
  
          Handle both numeric and UTC isoformat strings.