command -range NativeTraits :<line1>,<line2>call NativeTraits()

function! NativeTraits() range
    if match(getline(a:firstline), "has") == -1
        throw "This does not look like a has block"
    endif

    let range_has = a:firstline . "," . a:lastline
    exec range_has . "sm/metaclass.*=>.*Collection::\\(\\w\\+\\).*,/traits => ['\\1'],/"

    call cursor(a:firstline, 0)
    let pfirst = search('provides\s*=>\s*{', "nW", a:lastline)

    call cursor(pfirst, 0)
    let plast = search('^\s*}', "nW", a:lastline)
    let range_prov = pfirst . "," . plast

    exec range_prov . "sm/\\(\\w\\+\\)\\s*=>\\s*'\\(\\w\\+\\)'/\\2 => '\\1'/"
    exec range_prov . "s/provides/handles/"
endfunction