You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: csv.rb
    path of file: ./repos/powerstation/powerstation/lib/compiled-jruby/lib/ruby/stdlib
    
    the code of the file until where you have to start completion: # encoding: US-ASCII
# = csv.rb -- CSV Reading and Writing
#
#  Created by
    
    def field(header_or_index, minimum_index = 0)
      # locate the pair
      finder = header_or_index.is_a?(Integer) ? :[] : :assoc
      pair   = @row[minimum_index..-1].send(finder, header_or_index)

      # return the field if we have a pair
      pair.nil? ? nil : pair.last
    end