in bigtable/src/main/scala/magnolify/bigtable/BigtableType.scala [114:120]
private def key(prefix: String, label: String): String =
if (prefix == null) label else s"$prefix.$label"
private def columnFilter(key: String): (String, Column) => Boolean = {
val recordKey = key + "."
(name: String, _: Column) => name == key || name.startsWith(recordKey)
}