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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 effective_len(self):
 """ Get the length of the sequence if N's are disregarded. """

    if self._effective_len is None:
      self._effective_len = len([nuc for nuc in self.sequenceData
                                 if nuc != "N" and nuc != "n"])
    return self._effective_len