code: def apply_uncertainty(self, value, source):
          
          if not self.filter_source(source):
              # source didn't pass the filter
              return 0
          if self.uncertainty_type in MFD_UNCERTAINTY_TYPES:
              self._apply_uncertainty_to_mfd(source.mfd, value)
          elif self.uncertainty_type in GEOMETRY_UNCERTAINTY_TYPES:
              self._apply_uncertainty_to_geometry(source, value)
          else:
              raise AssertionError("unknown uncertainty type '%s'"
                                   % self.uncertainty_type)
          return 1
docs: Apply this branchset's uncertainty with value ``value`` to source
          ``source``, if it passes :meth:`filters <filter_source>`.
  
          This method is not called for uncertainties of types "gmpeModel"
          and "sourceModel".
  
          :param value:
              The actual uncertainty value of :meth:`sampled <sample>` branch.
              Type depends on uncertainty type.
          :param source:
              The opensha source data object.
          :return:
              0 if the source was not changed, 1 otherwise