fix piracy with DataLoader (#2608)

* fix piracy

* fix test

* Update test/Project.toml

Author: CarloLucibello

src/devices.jl

@@ -2,14 +2,3 @@ get_device(x) = MLDataDevices.get_device(x)
 
 @doc (@doc MLDataDevices.get_device) get_device
 
-function (device::MLDataDevices.AbstractDevice)(d::MLUtils.DataLoader)
-    MLUtils.DataLoader(MLUtils.mapobs(device, d.data),
-        d.batchsize,
-        d.buffer,
-        d.partial,
-        d.shuffle,
-        d.parallel,
-        d.collate,
-        d.rng,
-    )
-end

src/functor.jl

@@ -179,72 +179,3 @@ Chain(
 ```
 """
 f16(m) = _paramtype(Float16, m)
-
-
-"""
-    gpu(data::DataLoader)
-    cpu(data::DataLoader)
-
-Transforms a given `DataLoader` to apply `gpu` or `cpu` to each batch of data,
-when iterated over. (If no GPU is available, this does nothing.)
-
-# Example
-
-```julia-repl
-julia> dl = Flux.DataLoader((x = ones(2,10), y='a':'j'), batchsize=3)
-4-element DataLoader(::NamedTuple{(:x, :y), Tuple{Matrix{Float64}, StepRange{Char, Int64}}}, batchsize=3)
-  with first element:
-  (; x = 2×3 Matrix{Float64}, y = 3-element StepRange{Char, Int64})
-
-julia> first(dl)
-(x = [1.0 1.0 1.0; 1.0 1.0 1.0], y = 'a':1:'c')
-
-julia> c_dl = gpu(dl)
-4-element DataLoader(::MLUtils.MappedData{:auto, typeof(gpu), NamedTuple{(:x, :y), Tuple{Matrix{Float64}, StepRange{Char, Int64}}}}, batchsize=3)
-  with first element:
-  (; x = 2×3 CuArray{Float32, 2, CUDA.Mem.DeviceBuffer}, y = 3-element StepRange{Char, Int64})
-
-julia> first(c_dl).x
-2×3 CuArray{Float32, 2, CUDA.Mem.DeviceBuffer}:
- 1.0  1.0  1.0
- 1.0  1.0  1.0
-```
-
-For large datasets, this is preferred over moving all the data to
-the GPU before creating the `DataLoader`, like this:
-
-```julia-repl
-julia> Flux.DataLoader((x = ones(2,10), y=2:11) |> gpu, batchsize=3)
-4-element DataLoader(::NamedTuple{(:x, :y), Tuple{CuArray{Float32, 2, CUDA.Mem.DeviceBuffer}, UnitRange{Int64}}}, batchsize=3)
-  with first element:
-  (; x = 2×3 CUDA.CuArray{Float32, 2, CUDA.Mem.DeviceBuffer}, y = 3-element UnitRange{Int64})
-```
-
-!!! warning
-    This only works if `gpu` is applied directly to the `DataLoader`.
-    While `gpu` acts recursively on Flux models and many basic Julia structs,
-    it will not work on (say) a tuple of `DataLoader`s.
-"""
-function gpu(d::MLUtils.DataLoader)
-  MLUtils.DataLoader(MLUtils.mapobs(gpu, d.data);
-    d.batchsize,
-    d.buffer,
-    d.partial,
-    d.shuffle,
-    d.parallel,
-    d.collate,
-    d.rng,
-  )
-end
-
-function cpu(d::MLUtils.DataLoader)
-  MLUtils.DataLoader(MLUtils.mapobs(cpu, d.data);
-    d.batchsize,
-    d.buffer,
-    d.partial,
-    d.shuffle,
-    d.parallel,
-    d.collate,
-    d.rng,
-  )
-end

test/data.jl

@@ -14,7 +14,6 @@
     @test batches[3] == X[:,5:5]
 
     d_cpu = d |> cpu  # does nothing but shouldn't error
-    @test d_cpu isa DataLoader
     @test first(d_cpu) == X[:,1:2]
     @test length(d_cpu) == 3