最近，我從Universal Robots安裝了離線模擬器，install.sh 結果刪除了我的整個ROS安裝。好。我按照官方指南重新安裝了它，現在rqt_graph不起作用：usr@legion:~/Documents/catkin_ws$ rqt_graphTraceback (most recent call last):  File "/opt/ros/melodic/bin/rqt_graph", line 5, in <module>    from rqt_gui.main import Main  File "/opt/ros/melodic/lib/python2.7/dist-packages/rqt_gui/main.py", line 41, in <module>    import rospy  File "/opt/ros/melodic/lib/python2.7/dist-packages/rospy/__init__.py", line 49, in <module>    from .client import spin, myargv, init_node, \  File "/opt/ros/melodic/lib/python2.7/dist-packages/rospy/client.py", line 60, in <module>    import rospy.impl.init  File "/opt/ros/melodic/lib/python2.7/dist-packages/rospy/impl/init.py", line 58, in <module>    from rosgraph.rosenv import DEFAULT_MASTER_PORT  # default port for master's to bind toImportError: cannot import name DEFAULT_MASTER_PORT（roscore 正在另一個終端中運行）我嘗試了 sudo apt install ros-melodic-rqt 和 sudo apt-get install python-rosgraph，但錯誤仍然存在。我挖掘并發現這個特定的變量已被添加到旋律分布中的該文件中，因此可能存在版本沖突，但我不知道如何檢查。如何進行？