Android Kotlin Room错误：实体和POJO应具有构造函数

请不要将此标记为重复，我见过其他类似的帖子，但没有任何帮助

我的实体：

@Entity(tableName = "batch_table")
data class Batch(
    val batch_id: String? ="",
    val batch_name: String? ="",
    val user_m_id: String? ="",
    val user_profile_id: String? =""
){
    @PrimaryKey(autoGenerate = true)
    var id1: Int? = 0
constructor():this("","","","")
}

我的刀：

@Dao
interface BatchDao{

    @Insert
    suspend fun insert(batch : MutableList<Batch>)

    @Query("delete from batch_table")
    suspend fun deleteBatchTable()

    @Query(" select * from batch_table ")
    suspend fun getAllBatches() :List<Batch>

    @Query("select batch_name from batch_table where batch_id = :batch_id")
    suspend fun getBatchName(batch_id:String)

    @Transaction
    suspend fun insertBatches(batch: MutableList<Batch>){
        deleteBatchTable()
        insert(batch)
    }

---

我忘了写函数的返回类型，但是抛出的错误指向了另一个东西，所以我感到困惑

 @Query("select batch_name from batch_table where batch_id = :batch_id")
    suspend fun getBatchName(batch_id:String) : String

 @Query("select batch_name from batch_table where batch_id = :batch_id")
    suspend fun getBatchName(batch_id:String) : String