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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def parse(self, valstr):
        # type: (bytes) -> None
        '''
        Parse an El Torito section header from a string.

        Parameters:
         valstr - The string to parse.
        Returns:
         Nothing.
        '''
        if self._initialized:
            raise pycdlibexception.PyCdlibInternalError('El Torito Section Header already initialized')

        (self.header_indicator, self.platform_id, self.num_section_entries,
         self.id_string) = struct.unpack_from(self.FMT, valstr, 0)

        self._initialized = True