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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 update_dvs(dvs_ref, dvs_config_spec):
    '''
    Updates a distributed virtual switch with the config_spec.

    dvs_ref
        The DVS reference.

    dvs_config_spec
        The updated config spec (vim.VMwareDVSConfigSpec) to be applied to
        the DVS.
    '''
    dvs_name = get_managed_object_name(dvs_ref)
    log.trace('Updating dvs \'%s\'', dvs_name)
    try:
        task = dvs_ref.ReconfigureDvs_Task(dvs_config_spec)
    except vim.fault.NoPermission as exc:
        log.exception(exc)
        raise salt.exceptions.VMwareApiError(
            'Not enough permissions. Required privilege: '
            '{0}'.format(exc.privilegeId))
    except vim.fault.VimFault as exc:
        log.exception(exc)
        raise salt.exceptions.VMwareApiError(exc.msg)
    except vmodl.RuntimeFault as exc:
        log.exception(exc)
        raise salt.exceptions.VMwareRuntimeError(exc.msg)
    wait_for_task(task, dvs_name, six.text_type(task.__class__))