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# T4257: Discussion on changing BGP autonomous system number syntax

from vyos.configtree import ConfigTree

def migrate(config: ConfigTree) -> None:
    # Check if BGP is even configured. Then check if local-as exists, then add the system-as, then remove the local-as. This is for global configuration.
    if config.exists(['protocols', 'bgp']):
        if config.exists(['protocols', 'bgp', 'local-as']):
            config.rename(['protocols', 'bgp', 'local-as'], 'system-as')

    # Check if vrf names are configured. Then check if local-as exists inside of a name, then add the system-as, then remove the local-as. This is for vrf configuration.
    if config.exists(['vrf', 'name']):
        for vrf in config.list_nodes(['vrf', 'name']):
            if config.exists(['vrf', f'name {vrf}', 'protocols', 'bgp', 'local-as']):
                config.rename(['vrf', f'name {vrf}', 'protocols', 'bgp', 'local-as'], 'system-as')