# File lib/csv.rb, line 83
  def CSV.open(path, mode, fs = nil, rs = nil, &block)
    if mode == 'r' or mode == 'rb'
      open_reader(path, mode, fs, rs, &block)
    elsif mode == 'w' or mode == 'wb'
      open_writer(path, mode, fs, rs, &block)
    else
      raise ArgumentError.new("'mode' must be 'r', 'rb', 'w', or 'wb'")
    end
  end