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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 get_fragment(self, offset):
 """ Get the part of the source which is causing a problem. """

        fragment_len = 10
        s = '%r' % (self.source[offset:offset + fragment_len])
        if offset + fragment_len < len(self.source):
            s += '...'
        return s