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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def update_descriptor_le(self, lineedit, tf):
 """Update the given line edit to show the descriptor that is stored in the index :param lineedit: the line edit to update with the descriptor :type lineedit: QLineEdit :param tf: the selected taskfileinfo :type tf: :class:`TaskFileInfo` | None :returns: None :rtype: None :raises: None """

        if tf:
            descriptor = tf.descriptor
            lineedit.setText(descriptor)
        else:
            lineedit.setText("")