Rename photo jsonify bytes_str, duration_str -> _string.

etiquette/objects.py

@@ -1077,9 +1077,9 @@ class Photo(ObjectBase):
             'ratio': self.ratio,
             'area': self.area,
             'bytes': self.bytes,
-            'duration_str': self.duration_string,
+            'duration_string': self.duration_string,
             'duration': self.duration,
-            'bytes_str': self.bytestring,
+            'bytes_string': self.bytestring,
             'has_thumbnail': bool(self.thumbnail),
             'created': self.created,
             'filename': self.basename,