<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def is_ordered(self):
 """ True if site is an ordered site, i.e., with a single species with occupancy 1. """

        totaloccu = self.species.num_atoms
        return totaloccu == 1 and len(self.species) == 1