prepare_header

# File lib/csv/writer.rb, line 63
    def prepare_header
      headers = @options[:headers]
      case headers
      when Array
        @headers = headers
        @use_headers = true
      when String
        @headers = CSV.parse_line(headers,
                                  col_sep: @options[:column_separator],
                                  row_sep: @options[:row_separator],
                                  quote_char: @options[:quote_character])
        @use_headers = true
      when true
        @headers = nil
        @use_headers = true
      else
        @headers = nil
        @use_headers = false
      end
      return unless @headers

      converter = @options[:header_fields_converter]
      @headers = converter.convert(@headers, nil, 0)
      @headers.each do |header|
        header.freeze if header.is_a?(String)
      end
    end