code: def _logpdf(self, **kwargs):
          
          if kwargs not in self:
              return -numpy.inf
          return self._lognorm + \
              numpy.log(self._dfunc(
                  numpy.array([kwargs[p] for p in self._params]))).sum()
docs: Returns the log of the pdf at the given values. The keyword
          arguments must contain all of parameters in self's params. Unrecognized
          arguments are ignored.