def kernel_sigma(n_kernels):
    """
    get sigmas for each guassian kernel.
    :param n_kernels: number of kernels(including the exact match)
    :return: sigmas, a list of sigma
    """
    sigmas = [0.001]  # exact match small variance means exact match ?
    if n_kernels == 1:
        return sigmas
    return sigmas + [0.1] * (n_kernels - 1)