docs: def _pass(self, step):
          """Check whether a :class:`~stagpy._step.Step` passes the filters."""
          okf = True
          okf = okf and (not self._flt['snap'] or step.isnap is not None)
          okf = okf and (not self._flt['rprof'] or step.rprof is not None)
          okf = okf and all(f in step.fields for f in self._flt['fields'])
          okf = okf and bool(self._flt['func'](step))
          return okf