in elitzur-avro/src/main/scala/com/spotify/elitzur/converters/avro/AvroConverter.scala [215:223]
override def toAvro(v: C[T], schema: Schema): Any = {
val c = implicitly[AvroConverter[T]]
// avro expects a list
val output: java.util.List[Any] = new java.util.ArrayList[Any]
toSeq(v).iterator.foreach(i => {
output.add(c.toAvro(i, schema.getElementType))
})
output
}