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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 avail_sizes(call=None):
    '''
    Return available Packet sizes.

    CLI Example:

    .. code-block:: bash

        salt-cloud --list-sizes packet-provider
        salt-cloud -f avail_sizes packet-provider
    '''
    if call == 'action':
        raise SaltCloudException(
            'The avail_locations function must be called with -f or --function.'
        )

    vm_ = get_configured_provider()

    manager = packet.Manager(auth_token=vm_['token'])

    ret = {}

    for plan in manager.list_plans():
        ret[plan.name] = plan.__dict__

    return ret