# File lib/facets/core/string/bracket.rb, line 15
  def bracket(bra, ket=nil)
    #ket = String.bra2ket[$&] if ! ket && /^[\[({<]$/ =~ bra
    ket = String.bra2ket[bra] unless ket
    "#{bra}#{self}#{ket ? ket : bra}"
  end