:param filename: File to check.
    :returns: True if it's a binary file, otherwise False.

def is_binary(filename):
    """
    :param filename: File to check.
    :returns: True if it's a binary file, otherwise False.
    """
    logger.debug('is_binary: %(filename)r', locals())

    # Check if the file extension is in a list of known binary types
    binary_extensions = ['pyc', 'iso', 'zip', 'pdf']
    for ext in binary_extensions:
        if filename.endswith(ext):
            return True

    # Check if the starting chunk is a binary string
    chunk = get_starting_chunk(filename)
    return is_binary_string(chunk)