Improve clips handling (#541)

* Improve clips handling

* Remove year, add extraType

* Don't bother refreshing for missing attribute

* Update with attributes found in payload

* Update docstrings for clips

Author: jjlawren

plexapi/video.py

@@ -10,7 +10,7 @@
 class Video(PlexPartialObject):
     """ Base class for all video objects including :class:`~plexapi.video.Movie`,
         :class:`~plexapi.video.Show`, :class:`~plexapi.video.Season`,
-        :class:`~plexapi.video.Episode`.
+        :class:`~plexapi.video.Episode`, :class:`~plexapi.video.Clip`.
 
         Attributes:
             addedAt (datetime): Datetime this item was added to the library.
@@ -774,24 +774,38 @@ def _defaultSyncTitle(self):
 
 @utils.registerPlexObject
 class Clip(Playable, Video):
-    """ Represents a single Clip."""
+    """Represents a single Clip.
+
+    Attributes:
+        TAG (str): 'Video'
+        TYPE (str): 'clip'
+        duration (int): Duration of movie in milliseconds.
+        extraType (int): Unknown
+        guid: Plex GUID (com.plexapp.agents.imdb://tt4302938?lang=en).
+        index (int): Plex index (?)
+        originallyAvailableAt (datetime): Datetime movie was released.
+        subtype (str): Type of clip
+        viewOffset (int): View offset in milliseconds.
+    """
 
     TAG = 'Video'
     TYPE = 'clip'
     METADATA_TYPE = 'clip'
 
     def _loadData(self, data):
-        self._data = data
-        self.addedAt = data.attrib.get('addedAt')
-        self.duration = data.attrib.get('duration')
+        """Load attribute values from Plex XML response."""
+        Video._loadData(self, data)
+        Playable._loadData(self, data)
+        self.duration = utils.cast(int, data.attrib.get('duration'))
+        self.extraType = utils.cast(int, data.attrib.get('extraType'))
         self.guid = data.attrib.get('guid')
-        self.key = data.attrib.get('key')
+        self.index = utils.cast(int, data.attrib.get('index'))
         self.originallyAvailableAt = data.attrib.get('originallyAvailableAt')
-        self.ratingKey = data.attrib.get('ratingKey')
-        self.skipDetails = utils.cast(int, data.attrib.get('skipDetails'))
         self.subtype = data.attrib.get('subtype')
-        self.thumb = data.attrib.get('thumb')
-        self.thumbAspectRatio = data.attrib.get('thumbAspectRatio')
-        self.title = data.attrib.get('title')
-        self.type = data.attrib.get('type')
-        self.year = data.attrib.get('year')
+        self.viewOffset = utils.cast(int, data.attrib.get('viewOffset', 0))
+
+    def section(self):
+        """Return the :class:`~plexapi.library.LibrarySection` this item belongs to."""
+        # Clip payloads currently do not contain 'librarySectionID'.
+        # Return None to avoid unnecessary attribute lookup attempts.
+        return None