Actually your example works because checks.py is in the same directory as agent.py, but say checks.py was in the preceeding directory, eg;
agent/agent.py
checks.py
Then you could do the following:
path = os.path.abspath(os.path.join(os.path.dirname(__file__), '..'))
if not path in sys.path:
sys.path.insert(1, path)
del path
Note the use of __file__
.