<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def checkSanity(cls, trust_root_string):
 """str -> bool is this a sane trust root? """

        trust_root = cls.parse(trust_root_string)
        if trust_root is None:
            return False
        else:
            return trust_root.isSane()