optimize the top level links call to be done only once

Author: syphax-bouazzouni

lib/ontologies_api_client/collection.rb

@@ -29,7 +29,8 @@ def method_missing(meth, *args, &block)
         ##
         # Get all top-level links for the API
         def top_level_links(link = LinkedData::Client.settings.rest_url)
-          HTTP.get(link)
+          @top_level_links ||= {}
+          @top_level_links[link] ||= HTTP.get(link)
         end
 
         ##