def canonical_names_from_filenames(db, filenames):
    """Convert filenames to the canonical form

    :Parameters:
        `db` : remembercases.TestbedEntityPropDB
        `filenames` : iterable yielding filenames

    :return: A list expressing the filenames in the canonical form.

    The canonical form is the relative path from the basepath in the db's
    default_tesbed, with dir separators always '/' irrespective of os.sep

    A typical example transformation is::
    
        ..\..\test\test_base.py -> test\test_base.py

    """
    return [ db.canonical_fname(s) for s in filenames ]