From 6663943eaebe0c947e459edc40e7af2a577be4f6 Mon Sep 17 00:00:00 2001
From: flaport <floris.laporte@gmail.com>
Date: Fri, 17 Nov 2023 10:15:20 -0800
Subject: [PATCH] bugfix of the bugfix

---
 fdtd/backend.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fdtd/backend.py b/fdtd/backend.py
index 497cda8..8639b4e 100644
--- a/fdtd/backend.py
+++ b/fdtd/backend.py
@@ -75,8 +75,12 @@ class Backend:
     def __repr__(self):
         return self.__class__.__name__
 
+    @staticmethod
     def is_complex(x):
         """check if an object is a `ComplexFloat`"""
+        import torch
+        import numpy as np
+
         return (
             isinstance(x, complex)
             or (isinstance(x, np.ndarray) and x.dtype in (np.complex64, np.complex128))