title: Why does setDuration not work inside QSequentialAnimationGroup?
body: <p>I have two QVariantAnimation stuffed into a QSequentialAnimationGroup and I'm trying to invert one of them. I tried to do it like this</p>
  
  <pre><code>self.animation_1 = QtCore.QVariantAnimation()
  self.animation_2 = QtCore.QVariantAnimation()
  
  self.animation_1.setDirection(QtCore.QVariantAnimation.Backward)
  self.animation_2.setDirection(QtCore.QVariantAnimation.Forward)
  
  self.group = QtCore.QSequentialAnimationGroup(self)
  self.group.addAnimation(self.animation_1)
  self.group.addAnimation(self.animation_2)
  </code></pre>
  
  <p>But it didn’t work. I tried so</p>
  
  <pre><code>self.group.setDirection(QtCore.QVariantAnimation.Backward)
  </code></pre>
  
  <p>But the whole animation is inverted. and I only need to invert one of them.
  I tried to do this by referring to the index</p>
  
  <pre><code>self.group.animationAt(0).setDirection(QtCore.QVariantAnimation.Backward)
  </code></pre>
  
  <p>Zero reactions. I also tried to do it like this</p>
  
  <pre><code>self.group.animationAt(self.group.indexOfAnimation(animation_1)).setDirection(QtCore.QVariantAnimation.Backward)
  </code></pre>
  
  <p>It still didn't help.</p>
  
  <p>How to do it?</p>
  
  <p>My code</p>
  
  <pre><code>import sys
  
  from PyQt5 import QtCore, QtGui, QtWidgets
  
  
  class Main(QtWidgets.QWidget):
      def __init__(self):
          super().__init__()
          block = QtWidgets.QWidget(self)
          block.setObjectName(u"block")
          block.setMinimumSize(QtCore.QSize(300, 300))
          self.block_but = QtWidgets.QWidget(block)
          self.block_but.setObjectName(u"block_but")
          self.block_but.setGeometry(QtCore.QRect(110, 20, 111, 111))
          move_blur_button_lay = QtWidgets.QVBoxLayout(self.block_but)
          move_blur_button_lay.setObjectName(u"move_blur_button_lay")
          self.menu_arr = []
  
          radio = QtWidgets.QPushButton(self.block_but)
          radio.setText('click me')
          radio.setObjectName("mv_radio_but")
          radio.pressed.connect(self.menu_animation)
          move_blur_button_lay.addWidget(radio)
          for x in range(2):
              menu = QtWidgets.QWidget(block)
              menu.resize(50, 60)
              menu._expand = False
              self.menu_arr.append(menu)
          self.menu_arr[0].setStyleSheet("""background:#ff0""")
  
          self.animation = []
          for i in range(2):
              menuAnimation = QtCore.QVariantAnimation()
              menuAnimation.setDuration(500)
              menuAnimation.setEasingCurve(QtCore.QEasingCurve.OutQuart)
              menuAnimation.setStartValue(QtCore.QPoint(-20, 10))
              menuAnimation.setEndValue(QtCore.QPoint(0, 10))
              self.animation.append(menuAnimation)
          self.group = QtCore.QSequentialAnimationGroup(self)
  
      def menu_animation(self):
          for c in range(2):
              pos1 = QtCore.QPoint(0, 0)
              pos2 = QtCore.QPoint(100, 0)
              self.animation[c].setStartValue(pos1)
              self.animation[c].setEndValue(pos2)
              self.animation[c].setDirection(QtCore.QAbstractAnimation.Backward)
              self.animation[c].valueChanged.connect(
                  lambda value, val=c: self.fun(value, val)
              )
          #self.animation[0].setDirection(QtCore.QVariantAnimation.Backward)
          #self.animation[1].setDirection(QtCore.QVariantAnimation.Forward)
  
          self.animation[0].setStartValue(pos1) 
          self.animation[0].setEndValue(pos2) 
          self.animation[1].setStartValue(pos2) 
          self.animation[1].setEndValue(pos1)
  
  
  
  
          self.group.addAnimation(self.animation[0])
          self.group.addAnimation(self.animation[1])
          self.group.start()
  
      def fun(self, value, val=""):
          self.menu_arr[val].move(value.x(), 0)
  
  
  StyleSheet = """
  QWidget QWidget,
  QWidget QWidget QWidget QWidget,
  QWidget QWidget QWidget QWidget QWidget QWidget,
  QWidget QWidget QWidget QWidget QWidget QWidget QWidget QWidget,
  QWidget QWidget QWidget QWidget QWidget QWidget QWidget QWidget QWidget QWidget{
  background:#000;
  color:#fff;
  }
  QWidget,
  QWidget QWidget QWidget,
  QWidget QWidget QWidget QWidget QWidget,
  QWidget QWidget QWidget QWidget QWidget QWidget QWidget,
  QWidget QWidget QWidget QWidget QWidget QWidget QWidget QWidget QWidget{
  background:#fff;
  color:#000;
  }
  """
  
  if __name__ == "__main__":
      app = QtWidgets.QApplication(sys.argv)
      app.setStyleSheet(StyleSheet)
      w = Main()
      w.resize(640, 570)  
      w.show()
      sys.exit(app.exec_())
  </code></pre>
  
  <p>What I want to get</p>
  
  <p><a href="https://i.stack.imgur.com/8RD89.gif" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/8RD89.gif" alt="enter image description here"></a></p>