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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 atlas_revalidate_peers( con=None, path=None, now=None, peer_table=None ):
 """ Revalidate peers that are older than the maximum peer age. Ping them, and if they don't respond, remove them. """

    global MIN_PEER_HEALTH

    if now is None:
        now = time_now()

    old_peer_infos = atlasdb_get_old_peers( now, con=con, path=path )
    for old_peer_info in old_peer_infos:
        res = atlas_peer_getinfo( old_peer_info['peer_hostport'] )
        if not res:
            log.debug("Failed to revalidate %s" % (old_peer_info['peer_hostport']))
            if atlas_peer_is_whitelisted( old_peer_info['peer_hostport'], peer_table=peer_table ):
                continue

            if atlas_peer_is_blacklisted( old_peer_info['peer_hostport'], peer_table=peer_table ):
                continue

            if atlas_peer_get_health( old_peer_info['peer_hostport'], peer_table=peer_table ) < MIN_PEER_HEALTH:
                atlasdb_remove_peer( old_peer_info['peer_hostport'], con=con, path=path, peer_table=peer_table )
        
        else:
            # renew 
            atlasdb_renew_peer( old_peer_info['peer_hostport'], now, con=con, path=path )

    return True