def METHOD_NAME(self) -> List[str]:
    if self._cloud_provider == 'aws':
        regions = self.params.get('region_name')
    elif self._cloud_provider == 'gce':
        regions = self.params.get('gce_datacenter')
    elif self._cloud_provider == 'azure':
        regions = self.params.get('region_name')
    else:
        regions = []
    if isinstance(regions, list):
        return regions
    if isinstance(regions, str):
        return regions.split()
    else:
        return []