Use package-local wrapper type instead of extending Base (or other packages') methods on DataFrame

[tkelman]

Since https://github.com/sisl/BayesNets.jl/blob/5febf756d38194712cfb8c0c2294252931611afa/src/DiscreteBayesNet/tables.jl does a const Table = DataFrame, all method extensions on Table are global and change the behavior of other unrelated code that uses DataFrames, just from importing BayesNets whether or not it's using this package. This is discouraged.

If Table were instead a wrapper struct that delegated the relevant operations to a single DataFrame field, then you could define methods on BayesNets.Table however you like and not be at risk of changing any other code's behavior.

Same issue with

BayesNets.jl/src/ProbabilisticGraphicalModels/assignments.jl

Line 7 in 5febf75

Base.names(a::Assignment) = collect(keys(a))

and

BayesNets.jl/src/ProbabilisticGraphicalModels/nodenames.jl

Line 5 in 5febf75

Base.convert(::Type{NodeNames}, name::NodeName) = [name]

as well

and 3cd56dc#commitcomment-22494521 should probably be submitted upstream in DataFrames?

[tawheeler]

@mykelk - maybe this can be delegated to another SISLer?

[mykelk]

@hamzaelsaawy said he can handle these issues.

[tkelman]

Yep these have all come up in past discussions, probably easier to track all in one place though rather than a bit scattered