def _make_unique(self, coords):
        """
        Remove redundant entries from coordinate array

        INPUT parameter:
        coords : list of 2d-coordinate points (TColgp_Array1OfPnt2d, pythonOCC)

        OUTPUT:
        unique_coords : list of unique coordinates (TColgp_Array1OfPnt2d, pythonOCC)
        """

        # tolerance for comparisons
        index = None
        tol = self._tol_default * self.data.get('m_n')

        # upper and lower index of point-array
        upper_index = len(coords)
        lower_index = 0

        # remove redundant entries
        uniques = list()
        for index in range(lower_index, upper_index):
            unique = True
            for unique_point in uniques:
                if abs(coords[index][0] - unique_point[0]) < tol and abs(coords[index][1] - unique_point[1]) < tol:
                    unique = False
            if unique:
                uniques.append([coords[index][0], coords[index][1]])

        # copy list entries into coordinate array
        length_uniques = len(uniques)
        unique_coords = {}
        for index in range(lower_index, lower_index + length_uniques):
            if abs(uniques[index - 1][0]) > tol:
                unique_x = uniques[index - 1][0]
            else:
                unique_x = 0.0
            if abs(uniques[index - 1][1]) > tol:
                unique_y = uniques[index - 1][1]
            else:
                unique_y = 0.0
            if unique_x and unique_y:
                unique_coords.update({index: [unique_x, unique_y]})

        unique_coords.update({index + 1: [0.0, self.data['d_a'] / 2]})
        return unique_coords