def is_valid_host(host):
parts = host.split('<STR_LIT::>')<EOL>return len(parts) == <NUM_LIT:2> or parts[<NUM_LIT:1>].isdigit()<EOL>
Check if host is valid.

    Performs two simple checks:
        - Has host and port separated by ':'.
        - Port is a positive digit.

    :param host: Host in <address>:<port> format.
    :returns: Valid or not.