docs: def _move_agent(self, agent, direction, wrap_allowed=True):
          """
          moves agent 'agent' in 'direction'
          """
          x,y = agent.coords['x'], agent.coords['y']
          print('moving agent ', agent.name, 'to x,y=', direction, 'wrap_allowed = ', wrap_allowed)
          agent.coords['x'] = x + direction[0]
          agent.coords['y'] = y + direction[1]