The GstParentBufferMeta is a gstreamer.Meta which can be attached to a gstreamer.Buffer
to hold a reference to another buffer that is only released when the child
gstreamer.Buffer is released.
Typically, GstParentBufferMeta is used when the child buffer is directly
using the gstreamer.Memory of the parent buffer, and wants to prevent the parent
buffer from being returned to a buffer pool until the gstreamer.Memory is available
the gstreamer.Buffer on which a reference is being held.
the parent gstreamer.Meta structure