class Regexp::Expression::Sequence

def add_to(exp, params = {}, active_opts = {})
  sequence = construct(
    level:             exp.level,
    set_level:         exp.set_level,
    conditional_level: params[:conditional_level] || exp.conditional_level,
    ts:                params[:ts],
  )
  sequence.options = active_opts
  exp.expressions << sequence
  sequence
end