Add StatelessTableTransform

Author: juliohm

src/transforms.jl

@@ -57,6 +57,14 @@ This function is intended for developers of new types.
 """
 function revertmeta end
 
+"""
+    StatelessTableTransform
+
+This trait is useful to signal that we can [`reapply`](@ref) a transform
+"fitted" with training data to "test" data without relying on the `cache`.
+"""
+abstract type StatelessTableTransform <: TableTransform end
+
 """
     StatelessFeatureTransform
 
@@ -162,6 +170,9 @@ reapplymeta(::FeatureTransform, meta, mcache) = meta
 # STATELESS FALLBACKS
 # --------------------
 
+reapply(transform::StatelessTableTransform, table, cache) =
+  apply(transform, table) |> first
+
 reapply(transform::StatelessFeatureTransform, table, cache) =
   apply(transform, table) |> first