[gnome-music] Cleanup use of python static and class methods

[Vadim Rutkovsky <vrutkovsky src gnome org>]

commit 50bac83315bedf8486d5dc58392f2b47301552ea
Author: Peter Shinners <pete shinners org>
Date:   Mon Sep 7 09:09:19 2015 -0700

    Cleanup use of python static and class methods
    
    Several classmethods and methods switched to staticmethod. This is a minor Python cleanup. No 
functionality or logic changes.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=754654

 gnomemusic/albumArtCache.py |   12 ++++++------
 gnomemusic/playlists.py     |   14 +++++++-------
 gnomemusic/query.py         |    5 +++++
 3 files changed, 18 insertions(+), 13 deletions(-)
---
diff --git a/gnomemusic/albumArtCache.py b/gnomemusic/albumArtCache.py
index b3b6f3a..d1bd96a 100644
--- a/gnomemusic/albumArtCache.py
+++ b/gnomemusic/albumArtCache.py
@@ -97,13 +97,13 @@ class AlbumArtCache(GObject.GObject):
     }
 
     @classmethod
-    def get_default(self):
-        if not self.instance:
-            self.instance = AlbumArtCache()
-        return self.instance
+    def get_default(cls):
+        if not cls.instance:
+            cls.instance = AlbumArtCache()
+        return cls.instance
 
-    @classmethod
-    def get_media_title(self, media, escaped=False):
+    @staticmethod
+    def get_media_title(media, escaped=False):
         title = media.get_title()
         if title:
             if escaped:
diff --git a/gnomemusic/playlists.py b/gnomemusic/playlists.py
index e7e5cb6..a7aaaf8 100644
--- a/gnomemusic/playlists.py
+++ b/gnomemusic/playlists.py
@@ -83,8 +83,8 @@ class StaticPlaylists:
         self.RecentlyAdded.QUERY = Query.get_recently_added_songs()
         self.Favorites.QUERY = Query.get_favorite_songs()
 
-    @classmethod
-    def get_protected_ids(self):
+    @staticmethod
+    def get_protected_ids():
         return [str(cls.ID) for name, cls in inspect.getmembers(StaticPlaylists)
                 if inspect.isclass(cls) and not (name == "__class__")]
 
@@ -108,12 +108,12 @@ class Playlists(GObject.GObject):
         return '<Playlists>'
 
     @classmethod
-    def get_default(self, tracker=None):
-        if self.instance:
-            return self.instance
+    def get_default(cls, tracker=None):
+        if cls.instance:
+            return cls.instance
         else:
-            self.instance = Playlists()
-        return self.instance
+            cls.instance = Playlists()
+        return cls.instance
 
     @log
     def __init__(self):
diff --git a/gnomemusic/query.py b/gnomemusic/query.py
index b9ab38e..d09dff0 100644
--- a/gnomemusic/query.py
+++ b/gnomemusic/query.py
@@ -1038,6 +1038,7 @@ class Query():
 
         return query
 
+    @staticmethod
     def get_recently_played_songs():
             #TODO: or this could take comparison date as an argument so we don't need to make a date string 
in query.py...
             #TODO: set time interval somewhere? A settings file? (Default is maybe 2 weeks...?)
@@ -1073,6 +1074,7 @@ class Query():
 
             return query
 
+    @staticmethod
     def get_recently_added_songs():
         #TODO: or this could take comparison date as an argument so we don't need to make a date string in 
query.py...
         #TODO: set time interval somewhere? A settings file? (Default is maybe 2 weeks...?)
@@ -1108,6 +1110,7 @@ class Query():
 
         return query
 
+    @staticmethod
     def get_favorite_songs():
         query = """
     SELECT ?url
@@ -1395,6 +1398,7 @@ class Query():
 
         return query
 
+    @staticmethod
     def add_favorite(song_url):
         query = """
             INSERT {
@@ -1411,6 +1415,7 @@ class Query():
 
         return query
 
+    @staticmethod
     def remove_favorite(song_url):
         query = """
             DELETE {