<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_instance(cls, encoded_key):
 """Return an ApiAuth instance from an encoded key """


        login_str = base64.b64decode(encoded_key).decode('utf-8')
        usertoken, password = login_str.strip().split(':', 1)

        instance = cls(usertoken, password)

        return instance