def dM(self, k, t, param, Mkt, tips=None, gaps=None):
assert <NUM_LIT:0> <= k < self.ncats<EOL>assert ((param in self.freeparams) or (param == '<STR_LIT:t>') or (<EOL>param == self.distributedparam))<EOL>assert param not in self.distributionparams<EOL>return self._models[k].dM(t, param, Mkt, tips=tips, gaps=gaps)<EOL>
See docs for `DistributionModel` abstract base class.