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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 read_history_file(self, filename=None): 
        u'''Load a readline history file.'''
        if filename is None:
            filename = self.history_filename
        try:
            for line in open(filename, u'r'):
                self.add_history(lineobj.ReadLineTextBuffer(ensure_unicode(line.rstrip())))
        except IOError:
            self.history = []
            self.history_cursor = 0