<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get(cls, scope=None):
 """Return default or predefined URLs from keyword, pass through ``scope``."""

        if scope is None:
            scope = cls.default
        if isinstance(scope, string_types) and scope in cls._keywords:
            return getattr(cls, scope)
        return scope