'Fetch a list of all network interfaces from all data centers.
:return:    ``list`` of class ``ProfitBricksNetworkInterface``
:rtype:     `list`'

def ex_list_network_interfaces(self):

    nodes = self.list_nodes()
    nics = list()
    for node in nodes:
        action = node.extra['entities']['nics']['href']
        nics += self._to_interfaces(self.connection.request(action=action, params={'depth': 1}, method='GET', with_full_url=True).object)
    return nics
