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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 _fetch_headers(self):
 """Needs ._fh handle to stream to be set by child"""

    self._header_text, self._n_ref = self._read_top_header()
    self._ref_lengths, self._ref_names = self._read_reference_information()
    self._header = SAMHeader(self._header_text)