Allow loading annotations of files without the db object

bob/pad/face/database/database.py

 from bob.pad.base.database import PadFile
 import bob.bio.video
+import bob.io.video
+from bob.db.base.annotations import read_annotation_file
 
 
 class VideoPadFile(PadFile):
@@ -9,14 +11,15 @@ class VideoPadFile(PadFile):
 
     def __init__(self, attack_type, client_id, path, file_id=None):
         super(VideoPadFile, self).__init__(
-            attack_type=attack_type,
-            client_id=client_id,
-            path=path,
-            file_id=file_id,
+            attack_type=attack_type, client_id=client_id, path=path, file_id=file_id
         )
 
-    def load(self, directory=None, extension='.avi',
-             frame_selector=bob.bio.video.FrameSelector(selection_style='all')):
+    def load(
+        self,
+        directory=None,
+        extension=".avi",
+        frame_selector=bob.bio.video.FrameSelector(selection_style="all"),
+    ):
         """Loads the video file and returns in a :any:`bob.bio.video.FrameContainer`.
 
         Parameters
@@ -34,3 +37,97 @@ class VideoPadFile(PadFile):
             The loaded frames inside a frame container.
         """
         return frame_selector(self.make_path(directory, extension))
+
+    def check_original_directory_and_extension(self):
+        if not hasattr(self, "original_directory"):
+            raise RuntimeError(
+                "Please set the original_directory attribute of files in your "
+                "database's object method."
+            )
+        if not hasattr(self, "original_extension"):
+            raise RuntimeError(
+                "Please set the original_extension attribute of files in your "
+                "database's object method."
+            )
+
+    @property
+    def frames(self):
+        """Returns an iterator of frames in the video.
+        If your database video files need to be loaded in a special way, you need to
+        override this property.
+
+        Returns
+        -------
+        collection.Iterator
+            An iterator returning frames of the video.
+
+        Raises
+        ------
+        RuntimeError
+            In your database implementation, the original_directory and
+            original_extension attributes of the files need to be set when database's
+            object method is called.
+        """
+        self.check_original_directory_and_extension()
+        path = self.make_path(
+            directory=self.original_directory, extension=self.original_extension
+        )
+        return iter(bob.io.video.reader(path))
+
+    @property
+    def number_of_frames(self):
+        self.check_original_directory_and_extension()
+        path = self.make_path(
+            directory=self.original_directory, extension=self.original_extension
+        )
+        return bob.io.video.reader(path).number_of_frames
+
+    @property
+    def frame_shape(self):
+        """Returns the size of each frame in this database.
+        This implementation assumes all videos and frames have the same shape.
+        It's best to override this method in your database implementation and return
+        a constant.
+
+        Returns
+        -------
+        (int, int, int)
+            The (Channels, Height, Width) sizes.
+        """
+        self.check_original_directory_and_extension()
+        path = self.make_path(
+            directory=self.original_directory, extension=self.original_extension
+        )
+        frame = next(bob.io.video.reader(path))
+        return frame.shape
+
+    @property
+    def annotations(self):
+        """Reads the annotations
+        For this property to work, you need to set ``annotation_directory``,
+        ``annotation_extension``, and ``annotation_type`` attributes of the files when
+        database's object method is called.
+
+        Returns
+        -------
+        dict
+            The annotations as a dictionary.
+        """
+        if not (
+            hasattr(self, "annotation_directory")
+            and hasattr(self, "annotation_extension")
+            and hasattr(self, "annotation_type")
+        ):
+            raise RuntimeError(
+                "For this property to work, you need to set ``annotation_directory``, "
+                "``annotation_extension``, and ``annotation_type`` attributes of the "
+                "files when database's object method is called."
+            )
+
+        if self.annotation_directory is None:
+            return None
+
+        annotation_file = self.make_path(
+            directory=self.annotation_directory, extension=self.annotation_extension
+        )
+        return read_annotation_file(annotation_file, self.annotation_type)