docs: def dloglikarray(self):
          """Derivative of `loglik` with respect to `paramsarray`."""
          assert self.dparamscurrent, "dloglikarray requires paramscurrent == True"
          nparams = len(self._index_to_param)
          dloglikarray = scipy.ndarray(shape=(nparams,), dtype='float')
          for (i, param) in self._index_to_param.items():
              if isinstance(param, str):
                  dloglikarray[i] = self.dloglik[param]
              elif isinstance(param, tuple):
                  dloglikarray[i] = self.dloglik[param[0]][param[1]]
          return dloglikarray