def add(self, elem, replace=False):
        """Add a requirement.

        :param elem: a string or :class:`Requirement` instance.
        :param replace: if `True`, packages in the set with the same name will
            be removed first.
        """
        if isinstance(elem, text_type):
            elem = Requirement.coerce(elem)
        if replace and elem in self:
            self.remove(elem)
        super(Requirements, self).add(elem)
def draw_axis(img, charuco_corners, charuco_ids, board):
    vecs = np.load("./calib.npz")  # I already calibrated the camera
    mtx, dist, _, _ = [vecs[i] for i in ('mtx', 'dist', 'rvecs', 'tvecs')]
    ret, rvec, tvec = cv2.aruco.estimatePoseCharucoBoard(
        charuco_corners, charuco_ids, board, mtx, dist)
    if ret is not None and ret is True:
        cv2.aruco.drawAxis(img, mtx, dist, rvec, tvec, 0.1)