code: def verifyChain(self, anchors, untrusted=None):
          
          untrusted = untrusted or []
          for a in anchors:
              chain = Chain(self + untrusted, a)
              if len(chain) == 1:             # anchor only
                  continue
              # check that the chain does not exclusively rely on untrusted
              if any(c in chain[1:] for c in self):
                  for c in chain:
                      if c.remainingDays() < 0:
                          break
                  if c is chain[-1]:      # we got to the end of the chain
                      return chain
          return None
docs: Perform verification of certificate chains for that certificate.
          A list of anchors is required. The certificates in the optional
          untrusted list may be used as additional elements to the final chain.
          On par with chain instantiation, only one chain constructed with the
          untrusted candidates will be retained. Eventually, dates are checked.