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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def build_relational_field(self, field_name, relation_info):
 """ Create fields for forward and reverse relationships. """

        field_class = self.serializer_related_field
        field_kwargs = get_relation_kwargs(field_name, relation_info)

        to_field = field_kwargs.pop('to_field', None)
        if to_field and not relation_info.related_model._meta.get_field(to_field).primary_key:
            field_kwargs['slug_field'] = to_field
            field_class = self.serializer_related_to_field

        # `view_name` is only valid for hyperlinked relationships.
        if not issubclass(field_class, HyperlinkedRelatedField):
            field_kwargs.pop('view_name', None)

        return field_class, field_kwargs