verify agents passed to simulator by:
        1. checking for unique names
        2. TODO - other checks if needed

def _verify_agents(self):
        """
        verify agents passed to simulator by:
        1. checking for unique names
        2. TODO - other checks if needed
        """
        #print('verifying...')
        nmes = []
        for agt_num, a in enumerate(self.agents):
            #print('agent#', agt_num, 'is type', type(a))
            nmes.append(a.name)
        if len(nmes) == len(set(nmes)):
            return True
        print('Error - you need to pass unique list of agent names to simulator')
        return False