code: def check(self, topic, value):
          
          datatype_key = topic.meta.get('datatype', 'none')
          self._datatypes[datatype_key].check(topic, value)
          validate_dt = topic.meta.get('validate', None)
          if validate_dt:
              self._datatypes[validate_dt].check(topic, value)
docs: Checking the value if it fits into the given specification