code: def mousePressEvent(self, ev):
      if ev.buttons() == Qt.MiddleButton:
          self.middle_click = True
          self._startPos = ev.pos()
      super(AnnotationView, self).mousePressEvent(ev)
  
file_path: PaddleSeg/EISeg/eiseg/widget/view.py
imports: from qtpy import QtWidgets, QtCore, QtGui
  from qtpy.QtCore import Qt, QPointF
label_desc: Use image node_id 5 for calling the AnnotationView obj's underlying member method code with example usage: obj.mousePressEvent(ev) without return types