CSV::Parser#prepare_header

# File tmp/rubies/ruby-3.3.0/lib/csv/parser.rb, line 754
def prepare_header
  @return_headers = @options[:return_headers]

  headers = @options[:headers]
  case headers
  when Array
    @raw_headers = headers
    quoted_fields = [false] * @raw_headers.size
    @use_headers = true
  when String
    @raw_headers, quoted_fields = parse_headers(headers)
    @use_headers = true
  when nil, false
    @raw_headers = nil
    @use_headers = false
  else
    @raw_headers = nil
    @use_headers = true
  end
  if @raw_headers
    @headers = adjust_headers(@raw_headers, quoted_fields)
  else
    @headers = nil
  end
end