Weight transformation function for 2-section view

[pszufe]

Provide a weight transformation function in TwoSectionView constructor.

struct TwoSectionView{T<:Real} <: AbstractGraph{Int}
    h::Hypergraph{T}
    f::Function
end

We need to discuss/check

• what is the default function to calculate weights
• should the view behave like weighted/unweighted graph depending on the function
• provide documentation on how to materialize the view (for some scenarios constantly pulling the view for the data and calling the function each time will be very inefficient)

[bkamins]

This probably will be more efficient:

struct TwoSectionView{T<:Real, F<:Union{Function, Type}} <: AbstractGraph{Int}
    h::Hypergraph{T}
    f::F
end