def [](name)
      name = name.to_s
      entries.detect { |entry| entry.name.to_s == name }
    end
def [](name)
      name = name.to_s
      entries.detect { |entry| entry.name.to_s == name }
    end
Lookup an entry in the SubjectSet based on a given name

 @param [#to_s] name
   the name of the entry

 @return [Object, nil]
   the entry having the given name, or nil if not found

 @api private