mixin foo
  p.bar&attributes(attributes) One
  p.baz.quux&attributes(attributes) Two
  p&attributes(attributes) Three
  p.bar&attributes(attributes)(class="baz") Four

body
  +foo.hello
  +foo#world
  +foo.hello#world
  +foo.hello.world
  +foo(class="hello")
  +foo.hello(class="world")
  +foo
  +foo&attributes({class: "hello"})