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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 _meta_schema_factory(self, columns, model, class_mixin):
 """ Creates ModelSchema marshmallow-sqlalchemy :param columns: a list of columns to mix :param model: Model :param class_mixin: a marshamallow Schema to mix :return: ModelSchema """

        _model = model
        if columns:
            class MetaSchema(ModelSchema, class_mixin):
                class Meta:
                    model = _model
                    fields = columns
                    strict = True
                    sqla_session = self.datamodel.session
        else:
            class MetaSchema(ModelSchema, class_mixin):
                class Meta:
                    model = _model
                    strict = True
                    sqla_session = self.datamodel.session
        return MetaSchema