def METHOD_NAME(self, obj):
    """ Returns a dict with any of the following keys:
        - identifier (string)
        - extent (a four tuple of floats)
        - size (a two-tuple of ints)
        - projection (an integer or two-tuple of two strings (definition and format))
        - footprint (a django.contrib.gis.geos.MultiPolygon)
        - begin_time (a python datetime.datetime)
        - end_time (a python datetime.datetime)
        The argument obj is of an arbitrary type, the reader needs to 
        determine whether or not the type is supported and an exception 
        shall be raised if not.
    """
    pass