<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def credibleregions(self, probs):
 """ Calculates the credible regions. """


        return [brentq(lambda l:  self.pdf[self.pdf > l].sum() - p, 0.0, 1.0) for p in probs]