function _keyDown()
        {
            var filteredChoices;

            if (lxSelect.choicesViewMode === 'panes') {
                filteredChoices = Object.keys(lxSelect.panes[(lxSelect.panes.length - 1)]);
            } else {
                filteredChoices = $filter('filterChoices')(lxSelect.choices, lxSelect.filter, lxSelect.filterModel);
            }

            if (filteredChoices.length)
            {
                lxSelect.activeChoiceIndex += 1;

                if (lxSelect.activeChoiceIndex >= filteredChoices.length)
                {
                    lxSelect.activeChoiceIndex = 0;
                }
            }

            if (lxSelect.autocomplete)
            {
                LxDropdownService.open('dropdown-' + lxSelect.uuid, '#lx-select-selected-wrapper-' + lxSelect.uuid);
            }
        }
When the down key is pressed, select the next item of the most right opened pane (the first one if we are at
the bottom).