<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _validate_unique(self, create=True):
 """ Validate the unique constraints for the entity """

        # Build the filters from the unique constraints
        filters, excludes = {}, {}

        for field_name, field_obj in self.meta_.unique_fields:
            lookup_value = getattr(self, field_name, None)
            # Ignore empty lookup values
            if lookup_value in Field.empty_values:
                continue
            # Ignore identifiers on updates
            if not create and field_obj.identifier:
                excludes[field_name] = lookup_value
                continue
            filters[field_name] = lookup_value

        # Lookup the objects by the filters and raise error on results
        for filter_key, lookup_value in filters.items():
            if self.exists(excludes, **{filter_key: lookup_value}):
                field_obj = self.meta_.declared_fields[filter_key]
                field_obj.fail('unique',
                               entity_name=self.__class__.__name__,
                               field_name=filter_key)