怎么才能拿到这个方法编译，奇怪的是，火花隐式已经被导入了。
def loadDsFromHive[T <: Product](tableName: String, spark: SparkSession): Dataset[T] = {
import spark.implicits._
spark.sql(s"SELECT * FROM $tableName").as[T]
}
这是错误：
Unable to find encoder for type stored in a Dataset. Primitive types (Int, String, etc) and Product types (case classes) are supported by importing spark.implicits._ Support for serializing other types will be added in future releases.
[error] spark.sql(s"SELECT * FROM $tableName").as[T]
根据org. apache.lark.sql.SQLImplicits的源代码，您需要类型类TypeTag作为您的类型，以便隐式Encoder存在：
import scala.reflect.runtime.universe.TypeTag
def loadDsFromHive[T <: Product: TypeTag](tableName: String, spark: SparkSession): Dataset[T] = ...
