is_nucleotide and isnucleotide

[jeleclaire]

BiochemicalAlgorithms.jl/src/core/fragment.jl

Line 671 in 939b823

@inline function is_nucleotide(frag::Fragment)

and

BiochemicalAlgorithms.jl/src/core/fragment.jl

Line 432 in 939b823

@inline function isnucleotide(frag::Fragment)

are rather confusing.

Maybe, we can set the FragmentVariantType once at initialization?
And then choose one naming convention consistent to Julia /base/: isnothing, ismissing etc.