_evaluate() {
        if (typeof this.modelClass.session === "undefined") {
            throw new Error(
                [
                    `Tried to query the ${this.modelClass.modelName} model's table without a session. `,
                    "Create a session using `session = orm.session()` and use ",
                    `\`session["${this.modelClass.modelName}"]\` for querying instead.`,
                ].join("")
            );
        }
        if (!this._evaluated) {
            const { session, modelName: table } = this.modelClass;
            const querySpec = {
                table,
                clauses: this.clauses,
            };
            this.rows = session.query(querySpec).rows;
            this._evaluated = true;
        }
        return this.rows;
    }
Performs the actual database query.
@private
@return {Array} rows corresponding to the QuerySet's clauses