def _expand_interface_name(self, interface_brief):
        """
        Obtain the full interface name from the abbreviated name.

        Cache mappings in self.interface_map.
        """
        if self.interface_map.get(interface_brief):
            return self.interface_map.get(interface_brief)
        command = 'show int {}'.format(interface_brief)
        output = self._send_command(command)
        first_line = output.splitlines()[0]
        if 'line protocol' in first_line:
            full_int_name = first_line.split()[0]
            self.interface_map[interface_brief] = full_int_name
            return self.interface_map.get(interface_brief)
        else:
            return interface_brief
Obtain the full interface name from the abbreviated name.

        Cache mappings in self.interface_map.