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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 _find_docstring_line(self, start, end):
 """Find the row where a docstring starts in a function or class. This will search for the first match of a triple quote token in row sequence from the start of the class or function. Args: start: the row where the class / function starts. end: the row where the class / function ends. Returns: int: the row number where the docstring is found. """

        for i in range(start, end + 1):
            if i in self._tokenized_triple_quotes:
                return i
        return None