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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 _get_existing_logical_drives(raid_adapter):
 """Collect existing logical drives on the server. :param raid_adapter: raid adapter info :returns: existing_logical_drives: get logical drive on server """

    existing_logical_drives = []
    logical_drives = raid_adapter['Server']['HWConfigurationIrmc'][
        'Adapters']['RAIDAdapter'][0].get('LogicalDrives')
    if logical_drives is not None:
        for drive in logical_drives['LogicalDrive']:
            existing_logical_drives.append(drive['@Number'])

    return existing_logical_drives