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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 HashBuffer(self, buf):
 """Updates underlying hashers with a given buffer. Args: buf: A byte buffer (string object) that is going to be fed to the hashers. """

    for hasher in itervalues(self._hashers):
      hasher.update(buf)
      if self._progress:
        self._progress()

    self._bytes_read += len(buf)