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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 _traverse_unobserved(stream,negative_filter,of):
 """Go through a stream and print out anything not in observed set"""

  observed = set()
  for line in stream:
    name = PacBioReadName(_nameprog.match(line).group(1))
    if name.get_molecule() not in negative_filter: of.write(line)
    observed.add(name.get_molecule())
  return negative_filter|observed