In the left pane in the picture I executed this from a different python 3.7 container in the same docker network:

from prefect import flow
    @flow(name="Prefect 2.0 Flow")
    def flow_prefect():
        print("Hello Prefect 2.0!")
        import time
        time.sleep(5)
        print("Good Bye Prefect 2.0!")

    flow_prefect()