Called by create() used to determine resource pool

def _determine_resource_pool(session, vm_):
    '''
    Called by create() used to determine resource pool
    '''
    resource_pool = ''
    if 'resource_pool' in vm_.keys():
        resource_pool = _get_pool(vm_['resource_pool'], session)
    else:
        pool = session.xenapi.pool.get_all()
        if not pool:
            resource_pool = None
        else:
            first_pool = session.xenapi.pool.get_all()[0]
            resource_pool = first_pool
    pool_record = session.xenapi.pool.get_record(resource_pool)
    log.debug('resource pool: %s', pool_record['name_label'])
    return resource_pool