<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _write_header(self):
 """ Write out the table header """

        self._ostream.write(len(self._header) * "-" + "\n")
        self._ostream.write(self._header)
        self._ostream.write("\n")
        self._ostream.write(len(self._header) * "-" + "\n")