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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def remove_known_host(host, application_name, user=None):
 """Remove the entry in known_hosts for host. :param host: hostname to lookup in file. :type host: str :param application_name: Name of application eg nova-compute-something :type application_name: str :param user: The user that the ssh asserts are for. :type user: str """

    log('Removing SSH known host entry for compute host at %s' % host)
    cmd = ['ssh-keygen', '-f', known_hosts(application_name, user), '-R', host]
    subprocess.check_call(cmd)