CSV::Writer#prepare_header

# File tmp/rubies/ruby-3.0.5/lib/csv/writer.rb, line 77
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