def download_file(url, dest=None, chunk_size=1024, replace="ask",
                  label="Downloading {dest_basename} ({size:.2f}MB)",
                  expected_extension=None):
    """Download a file from a given URL and display progress.

    :param dest: If the destination exists and is a directory, the filename
        will be guessed from the Content-Disposition header. If the destination
        is an existing file, the user will either be prompted to overwrite, or
        the file will be replaced (depending on the value of **replace**). If
        the destination does not exist, it will be used as the filename.
    :param int chunk_size: bytes read in at a time.
    :param replace: If `False`, an existing destination file will not be
        overwritten.
    :param label: a string which is formatted and displayed as the progress bar
        label. Variables provided include *dest_basename*, *dest*, and *size*.
    :param expected_extension: if set, the filename will be sanitized to ensure
        it has the given extension. The extension should not start with a dot
        (`.`).
    """
    dest = Path(dest or url.split("/")[-1])
    response = get(url, stream=True)
    if (dest.exists()
            and dest.is_dir()
            and "Content-Disposition" in response.headers):
        content_disposition = rfc6266.parse_requests_response(response)
        if expected_extension is not None:
            filename = content_disposition.filename_sanitized(
                expected_extension)
        filename = secure_filename(filename)
        dest = dest / filename
    if dest.exists() and not dest.is_dir():
        if (replace is False
                or replace == "ask"
                and not click.confirm("Replace {}?".format(dest))):
            return str(dest)
    size = int(response.headers.get("content-length", 0))
    label = label.format(dest=dest, dest_basename=dest.name,
                         size=size/1024.0/1024)
    with click.open_file(str(dest), "wb") as f:
        content_iter = response.iter_content(chunk_size=chunk_size)
        with click.progressbar(content_iter, length=size/1024,
                               label=label) as bar:
            for chunk in bar:
                if chunk:
                    f.write(chunk)
                    f.flush()
    return str(dest)
def apply_ktst(K, y, iterations=10000, subjects=False, verbose=True):
    """
    Compute MMD^2_u, its null distribution and the p-value of the
    kernel two-sample test.

    Parameters:
    ----------
    K: array-like
        Kernel matrix
    y: array_like
        class labels
    verbose: bool
        Verbosity

    Returns:
    -------
    mmd2u: float
        MMD^2_u value.
    acc_null: array
        Null distribution of the MMD^2_u
    p_value: float
         p-value
    """
    assert len(np.unique(y)) == 2, 'KTST only works on binary problems'

    # Assuming that the first m rows of the kernel matrix are from one
    # class and the other n rows from the second class.
    m = len(y[y == 0])
    n = len(y[y == 1])
    mmd2u = MMD2u(K, m, n)
    if verbose:
        print("MMD^2_u = %s" % mmd2u)
        print("Computing the null distribution.")
    if subjects:
        perms = [permutation_subjects_ktst(y) for i in range(iterations)]
        mmd2u_null = compute_null_distribution_given_permutations(K, m, n,
                                                                  perms,
                                                                  iterations)
    else:
        mmd2u_null = compute_null_distribution(K, m, n, iterations,
                                               verbose=verbose)

    p_value = max(1.0/iterations, (mmd2u_null > mmd2u).sum()
                  / float(iterations))
    if verbose:
        print("p-value ~= %s \t (resolution : %s)" % (p_value, 1.0/iterations))

    return mmd2u, mmd2u_null, p_value