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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, vd, datastr, ino):
        # type: (headervd.PrimaryOrSupplementaryVD, bytes, inode.Inode) -> bool
        '''
        A method to parse a boot info table out of a string.

        Parameters:
         vd - The Volume Descriptor associated with this Boot Info Table.
         datastr - The string to parse the boot info table out of.
         ino - The Inode associated with the boot file.
        Returns:
         True if this is a valid El Torito Boot Info Table, False otherwise.
        '''
        if self._initialized:
            raise pycdlibexception.PyCdlibInternalError('This Eltorito Boot Info Table is already initialized')
        (pvd_extent, rec_extent, self.orig_len,
         self.csum) = struct.unpack_from('=LLLL', datastr, 0)

        if pvd_extent != vd.extent_location() or rec_extent != ino.extent_location():
            return False

        self.vd = vd
        self.inode = ino
        self._initialized = True

        return True