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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_fname_label(self):

 """Upadte file name label."""

        filename = to_text_string(self.get_current_filename())
        if len(filename) > 100:
            shorten_filename = u'...' + filename[-100:]
        else:
            shorten_filename = filename
        self.fname_label.setText(shorten_filename)