docs: def fit(self, X, y=None):
          """Calls the ctmc.ctmc function
  
          Parameters
          ----------
          X : list of lists
              (see ctmc function 'data')
  
          y
              not used, present for API consistence purpose.
          """
          self.transmat, self.genmat, self.transcount, self.statetime = ctmc(
              X, self.numstates, self.transintv, self.toltime, self.debug)
          return self