Before:
  runtime ale_linters/dafny/dafny.vim

After:
  call ale#linter#Reset()

Execute(The Dafny handler should parse output correctly):
  AssertEqual
  \ [
  \   {
  \     'bufnr': 0,
  \     'col': 45,
  \     'lnum': 123,
  \     'text': 'A precondition for this call might not hold.',
  \     'type': 'E'
  \   },
  \   {
  \     'bufnr': 0,
  \     'col': 90,
  \     'lnum': 678,
  \     'text': 'This is the precondition that might not hold.',
  \     'type': 'W'
  \   }
  \ ],
  \ ale_linters#dafny#dafny#Handle(0, [
  \ 'File.dfy(123,45): Error BP5002: A precondition for this call might not hold.',
  \ 'File.dfy(678,90): Related location: This is the precondition that might not hold.'
  \ ])