docs: def _reprJSON(self):
          """Returns a JSON serializable represenation of a ``PeptideSequence``
          class instance. Use :func:`maspy.proteindb.PeptideSequence._fromJSON()`
          to generate a new ``PeptideSequence`` instance from the return value.
  
          :returns: a JSON serializable python object
          """
          return {'__PepSeq__': [self.sequence, self.missedCleavage,
                                 self.isUnique, list(self.proteins),
                                 self.proteinPositions]}