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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 _init_file(self):
 """Initialise the file header. This will erase any data previously in the file."""

        header_length = 2*SECTOR_LENGTH
        if self.size > header_length:
            self.file.truncate(header_length)
        self.file.seek(0)
        self.file.write(header_length*b'\x00')
        self.size = header_length