def get_network_instances(self, name="<STR_LIT>"):
raise NotImplementedError<EOL>
Return a dictionary of network instances (VRFs) configured, including default/global

Args:
    name(string) - Name of the network instance to return, default is all.

Returns:
    A dictionary of network instances in OC format:
    * name (dict)
        * name (unicode)
        * type (unicode)
        * state (dict)
            * route_distinguisher (unicode)
        * interfaces (dict)
            * interface (dict)
                * interface name: (dict)

Example::

    {
        u'MGMT': {
            u'name': u'MGMT',
            u'type': u'L3VRF',
            u'state': {
                u'route_distinguisher': u'123:456',
            },
            u'interfaces': {
                u'interface': {
                    u'Management1': {}
                }
            }
        },
        u'default': {
            u'name': u'default',
            u'type': u'DEFAULT_INSTANCE',
            u'state': {
                u'route_distinguisher': None,
            },
            u'interfaces: {
                u'interface': {
                    u'Ethernet1': {}
                    u'Ethernet2': {}
                    u'Ethernet3': {}
                    u'Ethernet4': {}
                }
            }
        }
    }