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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 _proc_sparse(self, tarfile):
 """Process a GNU sparse header plus extra headers. """

        # We already collected some sparse structures in frombuf().
        structs, isextended, origsize = self._sparse_structs
        del self._sparse_structs

        # Collect sparse structures from extended header blocks.
        while isextended:
            buf = tarfile.fileobj.read(BLOCKSIZE)
            pos = 0
            for i in range(21):
                try:
                    offset = nti(buf[pos:pos + 12])
                    numbytes = nti(buf[pos + 12:pos + 24])
                except ValueError:
                    break
                if offset and numbytes:
                    structs.append((offset, numbytes))
                pos += 24
            isextended = bool(buf[504])
        self.sparse = structs

        self.offset_data = tarfile.fileobj.tell()
        tarfile.offset = self.offset_data + self._block(self.size)
        self.size = origsize
        return self