fold python hunter log files in vim

gistfile1.txt

function! Hunter()
    " It takes 2 mins to fold 400k lines in my macbook air.
    function! ColBase()
        " determine column number (3rd col, code part) in the first (base) line
        call cursor(1, 1)
        let mypattern = '\v(.+:\d+\s+\w+\s+!\s+\zs)|(.+:\d+\s+\w+\s+\zs)'

        let [lnum, colbase] = searchpos(mypattern, 'n')
        return colbase
    endfunction

    function! Info(lnum)
        " determine the 3rd column position ( code part)
        call cursor(a:lnum, 1)
        let mypattern = '\v(.+:\d+\s+\w+\s+!\s+\zs)|(.+:\d+\s+\w+\s+\zs)'
        let [lnum, col_pos] = searchpos(mypattern, 'n')
        " dterminte the 3rd col indentation
        let indentlevel = (col_pos - w:colbase) / 3
        let info = [col_pos, indentlevel]
        return info
    endfunction

    function! GetPotionFold(lnum)
        let info = Info(a:lnum)
        let colcode = info[0]
        let indentlevel = info[1]
        let current_content = getline(a:lnum)
        if current_content[colcode-1: colcode+1] ==# '=> '
            let tmp = indentlevel + 1
            return '>' . tmp
        endif
        if current_content[colcode-1: colcode+1] ==# '<= '
            let tmp = indentlevel + 1
            return tmp
        endif
        return indentlevel
    endfunction

    let w:colbase = ColBase()
    set foldmethod=expr
    set foldexpr=GetPotionFold(v:lnum)

    " change fold default color
    highlight Folded ctermbg=Black ctermfg=darkgray

    " render 3rd column color
    function! HunterColor()
        syntax include @Python syntax/python.vim 
        syntax region pythonCode matchgroup=SnipPy start=/\v^.+:\d+\s+\w+\s+/ end=/$/ contains=@Python keepend
        hi SnipPy ctermfg=darkgray guifg=darkgray
        hi Snip1 ctermfg=darkred guifg=darkred gui=bold
        hi Snip2 ctermfg=lightred guifg=lightred
        match Snip1 /\v\<\=\s\w+:/
        2match Snip2 /\v\=\>\s\w+/
    endfunction
    call HunterColor()

    " enable click    
    " set mouse=a
    set foldcolumn=8

endfunction

Put above code inside .vimrc
It is folding by syntax '=>' and '<=' and ignore '! exception'
usage:
:call Hunter()
It takes 2 mins to fold 400k lines in my macbook air.
If it is a large file, color of python code part may not be rendered. You need to redraw with CTRL-L

if you are beginner about folding
zo (o)pen the fold
zc (c)lose the fold

In non-gui vim, You might want to activate mouse action to click open/close the folds
set mouse=a
set foldcolumn=8

a friendly beginner tutorial about folding is covered inside vim docs
:help usr_28

If it is a large file, color of python part may not be rendered. you need to redraw with ctrl-L