def header_size(self):
        """Total size of `file`'s header (including extended) in bytes.

        The size of the header is determined from `header`. If this is not
        possible (i.e., before the header has been read), 0 is returned.

        If the header contains an ``'nsymbt'`` entry (size of the extra
        header in bytes), its value is added to the regular header size.
        """
        standard_header_size = MRC_HEADER_SIZE

        try:
            extra_header_size = int(self.header['nsymbt']['value'])
        except KeyError:
            extra_header_size = 0

        return standard_header_size + extra_header_size
Total size of `file`'s header (including extended) in bytes.

        The size of the header is determined from `header`. If this is not
        possible (i.e., before the header has been read), 0 is returned.

        If the header contains an ``'nsymbt'`` entry (size of the extra
        header in bytes), its value is added to the regular header size.