code: def verify(self, otp, for_time=None, valid_window=0):
          
          if for_time is None:
              for_time = datetime.datetime.now()
  
          if valid_window:
              for i in range(-valid_window, valid_window + 1):
                  if utils.strings_equal(str(otp), str(self.at(for_time, i))):
                      return True
              return False
  
          return utils.strings_equal(str(otp), str(self.at(for_time)))
docs: Verifies the OTP passed in against the current time OTP
          @param [String/Integer] otp the OTP to check against
          @param [Integer] valid_window extends the validity to this many counter ticks before and after the current one