Extract a list of all superclass names from a class definition dict.

def get_superclasses_from_class_definition(class_definition):
    """Extract a list of all superclass names from a class definition dict."""
    # New-style superclasses definition, supporting multiple-inheritance.
    superclasses = class_definition.get('superClasses', None)

    if superclasses:
        return list(superclasses)

    # Old-style superclass definition, single inheritance only.
    superclass = class_definition.get('superClass', None)
    if superclass:
        return [superclass]

    # No superclasses are present.
    return []