class Sass::Selector::Attribute

def to_s(opts = {})

Other tags:
    See: Selector#to_s -
def to_s(opts = {})
  res = "["
  res << @namespace << "|" if @namespace
  res << @name
  res << @operator << @value if @value
  res << " " << @flags if @flags
  res << "]"
end