def find_header_size(filename):
    """Script to find the header size of a filterbank file

    Args:
        filename (str): Name of file

    Returns size of header in Bytes (int)
    """
    filfile = open(filename, 'rb')
    filfile.seek(0)
    round1 = filfile.read(1000)
    headersize = round1.find('HEADER_END') + len('HEADER_END')
    return headersize
