'Function to check if a `Zone` object exists.
:param zone_id: ID of the `Zone` object.
:type zone_id: ``str``
:param zones_list: A list containing `Zone` objects.
:type zones_list: ``list``.
:rtype: Returns `True` or `False`.'

def ex_zone_exists(self, zone_id, zones_list):

    zone_ids = []
    for zone in zones_list:
        zone_ids.append(zone.id)
    return (zone_id in zone_ids)
