更改QTableWidget的branch展开符样式为“+“加号字符

 css的配置

tree_widget.setStyleSheet("QTreeView::branch:closed:has-children:has-siblings { border-image: none; image: none; }"
                         "QTreeView::branch:open:has-children:has-siblings { border-image: none; image: none; }"
                         "QTreeView::branch:closed:has-children:!has-siblings { border-image: none; image: none; }"
                         "QTreeView::branch:open:has-children:!has-siblings { border-image: none; image: none; }"
                         "QTreeView::branch:closed:!has-children:has-siblings { border-image: none; image: none; }"
                         "QTreeView::branch:open:!has-children:has-siblings { border-image: none; image: none; }"
                         "QTreeView::branch:closed:!has-children:!has-siblings { border-image: none; image: none; }"
                         "QTreeView::branch:open:!has-children:!has-siblings { border-image: none; image: none; }"
                         "QTreeView::branch:closed:has-children:has-siblings:adjoins-item { border-image: none; image: none; }"
                         "QTreeView::branch:open:has-children:has-siblings:adjoins-item { border-image: none; image: none; }"
                         "QTreeView::branch:closed:has-children:!has-siblings:adjoins-item { border-image: none; image: none; }"
                         "QTreeView::branch:open:has-children:!has-siblings:adjoins-item { border-image: none; image: none; }"
                         "QTreeView::branch:closed:!has-children:has-siblings:adjoins-item { border-image: none; image: none; }"
                         "QTreeView::branch:open:!has-children:has-siblings:adjoins-item { border-image: none; image: none; }"
                         "QTreeView::branch:closed:!has-children:!has-siblings:adjoins-item { border-image: none; image: none; }"
                         "QTreeView::branch:open:!has-children:!has-siblings:adjoins-item { border-image: none; image: none; }"
                         "QTreeView::branch:closed { qproperty-icon: '+'; }"
                         "QTreeView::branch:open { qproperty-icon: '-'; }")