# File lib/faster_csv.rb, line 1473
    def <<(row)
      # make sure headers have been assigned
      if header_row? and [Array, String].include? @use_headers.class
        parse_headers  # won't read data for Array or String
        self << @headers if @write_headers
      end

      # Handle FasterCSV::Row objects and Hashes
      row = case row
            when self.class::Row then row.fields
            when Hash            then @headers.map { |header| row[header] }
            else                      row
            end

      @headers =  row if header_row?
      @lineno  += 1

      @io << row.map(&@quote).join(@col_sep) + @row_sep  # quote and separate

      self  # for chaining
    end