CSV::FieldsConverter#add_converter

# File tmp/rubies/ruby-3.0.5/lib/csv/fields_converter.rb, line 23
def add_converter(name=nil, &converter)
  if name.nil?  # custom converter
    @converters << converter
  else          # named converter
    combo = @builtin_converters[name]
    case combo
    when Array  # combo converter
      combo.each do |sub_name|
        add_converter(sub_name)
      end
    else        # individual named converter
      @converters << combo
    end
  end
end