def METHOD_NAME(self, locs):
    """Compute initial traction at locations.
    """
    (npts, dim) = locs.shape
    traction = numpy.zeros((1, npts, self.SPACE_DIM), dtype=numpy.float64)
    traction[0,:, 0] = -sxy
    traction[0,:, 1] = 0.0
    traction[0,:, 2] = 0.0
    return traction