code: def exists(self, bucket, label):
          '''Whether a given bucket:label object already exists.'''
          fn = self._zf(bucket, label)
          try:
              self.z.getinfo(fn)
              return True
          except KeyError:
              return Falsf exists(self, bucket, label):
          '''Whether a given bucket:label object already exists.'''
          fn = self._zf(bucket, label)
          try:
              self.z.getinfo(fn)
              return True
          except KeyError:
              return False
docs: Whether a given bucket:label object already exists.