add ntimepoints

grouper.py

@@ -34,6 +34,10 @@ class Grouper(ABC):
     def fsignal(self):
         return list(self.signals.values())[0]
 
+    @property
+    def ntimepoints(self):
+        return max([s.ntimepoints for s in self.signals.values()])
+
     @property
     def siglist(self):
         return self.fsignal.siglist