I want to save a KDTree into the disk and reuse it again with JLD2, but ran into problem after loading it,

```
using NearestNeighbors
using FileIO, JLD2
kdtree = KDTree(rand(2, 100))
save("/tmp/test.jld2", "kdtree", kdtree) # it works
```

but I got warning when loading the saved one,

```
julia> kdt = load("/tmp/test.jld2", "kdtree");
┌ Warning: type StaticArrays.SArray{Tuple{2},Float64,1,2} does not exist in workspace; reconstructing
└ @ JLD2 ~/.julia/packages/JLD2/KjBIK/src/data.jl:1153
┌ Warning: type Distances.Euclidean does not exist in workspace; reconstructing
└ @ JLD2 ~/.julia/packages/JLD2/KjBIK/src/data.jl:1153
┌ Warning: type parameters for KDTree{getfield(JLD2.ReconstructedTypes, Symbol("##StaticArrays.SArray{Tuple{2},Float64,1,2}#366")),getfield(JLD2.ReconstructedTypes, Symbol("##Distances.Euclidean#367")),Float64} do not match type KDTree in workspace; reconstructing
└ @ JLD2 ~/.julia/packages/JLD2/KjBIK/src/data.jl:1133
```

and got an error when attempting to query with the loaded tree

```
julia> knn(kdt, [1, 2.0], 3)
ERROR: MethodError: no method matching knn(::getfield(JLD2.ReconstructedTypes, Symbol("##KDTree{getfield(JLD2.ReconstructedTypes, Symbol("##StaticArrays.SArray{Tuple{2},Float64,1,2}#366")),getfield(JLD2.ReconstructedTypes, Symbol("##Distances.Euclidean#367")),Float64}#368")), ::Array{Float64,1}, ::Int64)
Closest candidates are:
knn(::NNTree{V,P} where P<:Distances.Metric, ::AbstractArray{T<:Number,1}, ::Int64) where {V, T<:Number} at /Users/fineday/.julia/packages/NearestNeighbors/N7lgR/src/knn.jl:40
knn(::NNTree{V,P} where P<:Distances.Metric, ::AbstractArray{T<:Number,1}, ::Int64, ::Any) where {V, T<:Number} at /Users/fineday/.julia/packages/NearestNeighbors/N7lgR/src/knn.jl:40
knn(::NNTree{V,P} where P<:Distances.Metric, ::AbstractArray{T<:Number,1}, ::Int64, ::Any, ::Function) where {V, T<:Number} at /Users/fineday/.julia/packages/NearestNeighbors/N7lgR/src/knn.jl:40
...
Stacktrace:
[1] top-level scope at none:0
```

so what’s the proper way to save it?