def polar2cart(r, phi, center):
    """
    transforms polar coords [r,phi] into cartesian coords [x,y] in the frame of the lense center

    :param coord: set of coordinates
    :type coord: array of size (n,2)
    :param center: rotation point
    :type center: array of size (2)
    :returns:  array of same size with coords [x,y]
    :raises: AttributeError, KeyError
    """
    x = r*np.cos(phi)
    y = r*np.sin(phi)
    return x - center[0], y - center[1]
transforms polar coords [r,phi] into cartesian coords [x,y] in the frame of the lense center

    :param coord: set of coordinates
    :type coord: array of size (n,2)
    :param center: rotation point
    :type center: array of size (2)
    :returns:  array of same size with coords [x,y]
    :raises: AttributeError, KeyError