def _extract_header_value(line):
    """
    Extracts a key / value pair from a header line in an ODF file
    """
    if not line:
        return None
    halves = line.split('=')
    if len(halves) > 1:
        key = halves[0].strip()
        value = halves[1].strip()
        return {key: value}
    else:
        halves = line.split(':')
        key = halves[0].strip()
        value = halves[1].strip()
        return {key: value}
