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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 convert_cidr(cidr):
    '''
    returns the network address, subnet mask and broadcast address of a cidr address

    .. versionadded:: 2016.3.0

    CLI Example:

    .. code-block:: bash

        salt '*' network.convert_cidr 172.31.0.0/16
    '''
    ret = {'network': None,
           'netmask': None,
           'broadcast': None}
    cidr = calc_net(cidr)
    network_info = ipaddress.ip_network(cidr)
    ret['network'] = six.text_type(network_info.network_address)
    ret['netmask'] = six.text_type(network_info.netmask)
    ret['broadcast'] = six.text_type(network_info.broadcast_address)
    return ret