fix mypy

Author: NoureldinYosri

tunits/core/__init__.pyi

@@ -229,6 +229,8 @@ class Value(Generic[NumericalT], WithUnit, np.generic, SupportsIndex):
     real: 'Value'
     imag: 'Value'
 
+    # needed because np.generic declars __new__ as abstract.
+    def __new__(cls: type[T], *args: Any, **kwargs: Any) -> T: ...
     @classmethod
     def from_proto(cls: type[T], msg: tunits_pb2.Value) -> T: ...
     def to_proto(self, msg: tunits_pb2.Value | None = None) -> tunits_pb2.Value: ...