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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 to_positions(self):
 """ Converts fractional coordinates of trajectory into positions """

        if self.coords_are_displacement:
            cumulative_displacements = np.cumsum(self.frac_coords, axis=0)
            positions = self.base_positions + cumulative_displacements
            self.frac_coords = positions
            self.coords_are_displacement = False
        return