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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 set_row_positions(self):
 """creates a list of row positions for simpler manipulation"""

        self.row_positions = [i * self.row_height for i in range(len(self.rows))]
        self.set_size_request(0, self.row_positions[-1] + self.row_height if self.row_positions else 0)