Minor change in gathering of registry keys for devices

Instead of appending keys into a list and then convert it into a set, keys are
stored directly into a set.

SystemInformation.py

@@ -42,7 +42,7 @@ class SystemInformation:
             'ProcessorNameString')
 
     def _graphics(self):
-        reg_keys = []
+        reg_keys = set()
         for device in range(16):
             try:
                 video_card_string = get_registry_value(
@@ -57,12 +57,12 @@ class SystemInformation:
                     '{}\\Video'.format(reg_key),
                     'Service')
                 if service == 'vga':
-                    reg_keys.append(reg_key)
+                    reg_keys.add(reg_key)
             except:
                 pass
 
         video_cards = []
-        for video_card in set(reg_keys):
+        for video_card in reg_keys:
             device_descrption = get_registry_value(
                 'HKEY_LOCAL_MACHINE',
                 'SYSTEM\\CurrentControlSet\\Control\\Video\\'