def enum_by_group(group)
      Enumerator.new(self, Proc.new { |field| field.group?(group) })
    end
def enum_by_group(group)
      Enumerator.new(self, Proc.new { |field| field.group?(group) })
    end
Returns an Enumerator for each Field for which #group?(+group+) is true.

 For example, to print all the fields, sorted by group, you could do:

   card.groups.sort.each do |group|
     card.enum_by_group(group).each do |field|
       puts "#{group} -> #{field.name}"
     end
   end

 or to get an array of all the fields in group "AGROUP", you could do:

   card.enum_by_group("AGROUP").to_a