diff --git a/src/pyGroupedTransforms/GroupedTransform.py b/src/pyGroupedTransforms/GroupedTransform.py
index 57bf99a..da40e01 100644
--- a/src/pyGroupedTransforms/GroupedTransform.py
+++ b/src/pyGroupedTransforms/GroupedTransform.py
@@ -1,12 +1,11 @@
 import numpy as np
+import pykeops
 import torch
+from pykeops.torch import LazyTensor
 
 from pyGroupedTransforms import *
-from .NFFTtools import index_set_without_zeros
-
-import pykeops
-from pykeops.torch import LazyTensor
 
+from .NFFTtools import index_set_without_zeros
 
 # All code that is linked to NFMTtools or to system = "mixed" is not tested yet....
 
@@ -272,13 +271,12 @@ def __init__(
                         bandwidths=s.bandwidths, X=np.copy(X[:, u], order="C")
                     )
         elif algorithm == "keops":
-            self.matrix = np.empty((0,0), dtype=object)
-            
+            self.matrix = np.empty((0, 0), dtype=object)
+
             self.transforms = [
-                DeferredLinearOperator()
-                for _ in range(len(self.settings))
+                DeferredLinearOperator() for _ in range(len(self.settings))
             ]
-            
+
             D = X.shape[1]
 
             freq_list = []
@@ -287,9 +285,8 @@ def __init__(
 
                 if len(s.bandwidths) == 0:
                     full = np.zeros((1, D), dtype=np.int32)
-                    
-                    
-                else: 
+
+                else:
                     local = index_set_without_zeros(
                         np.array(s.bandwidths, dtype=np.int32)
                     ).T
@@ -302,15 +299,11 @@ def __init__(
                 freq_list.append(full)
 
             freq = np.vstack(freq_list)
-            
+
             X_torch = torch.tensor(X, dtype=torch.float64, device="cuda")
-            I_torch = torch.tensor(
-                freq,
-                dtype=torch.float64,
-                device="cuda"
-            )
-            
-            def trafo(fhat): 
+            I_torch = torch.tensor(freq, dtype=torch.float64, device="cuda")
+
+            def trafo(fhat):
                 X_i = LazyTensor(X_torch[:, None, :].contiguous())
                 K_j = LazyTensor(I_torch[None, :, :].contiguous())
                 phase_fwd = (X_i * K_j).sum(-1)
@@ -327,15 +320,19 @@ def trafo(fhat):
                 except Exception as e:
                     print("Error in KeOps trafo:", e)
                     return None
-                
+
             def adjoint(f):
-                f_torch = torch.tensor(f, dtype=torch.complex128, device="cuda").contiguous()
-                
+                f_torch = torch.tensor(
+                    f, dtype=torch.complex128, device="cuda"
+                ).contiguous()
+
                 X_i = LazyTensor(X_torch[None, :, :].contiguous())
                 K_j = LazyTensor(I_torch[:, None, :].contiguous())
 
                 phase = (K_j * X_i).sum(-1)
-                kernel = (-2*torch.pi*phase).cos() - 1j*(-2*torch.pi*phase).sin()
+                kernel = (-2 * torch.pi * phase).cos() - 1j * (
+                    -2 * torch.pi * phase
+                ).sin()
 
                 f_i = LazyTensor(f_torch[None, :, None].contiguous())
 
@@ -343,16 +340,21 @@ def adjoint(f):
                     result = (kernel * f_i).sum(dim=1)
                     torch.cuda.synchronize()
                     result = result.squeeze().cpu().numpy()
-                
+
                     return result
                 except Exception as e:
                     print("Error in KeOps adjoint:", e)
                     return None
 
-            self.transforms = [DeferredLinearOperator(
-                dtype=np.complex128, shape=(X.shape[0], len(freq)), mfunc=trafo, rmfunc=adjoint
-            )]
-    
+            self.transforms = [
+                DeferredLinearOperator(
+                    dtype=np.complex128,
+                    shape=(X.shape[0], len(freq)),
+                    mfunc=trafo,
+                    rmfunc=adjoint,
+                )
+            ]
+
         else:
             self.transforms = []
             s1 = self.settings[0]
@@ -432,15 +434,15 @@ def adjoint_worker(i):
                         adjoint_worker(i)
 
                 return fhat
-            
+
             elif self.algorithm == "keops":
-                return GroupedCoefficients(self.settings, self.transforms[0].H @ other)  
-             
+                return GroupedCoefficients(self.settings, self.transforms[0].H @ other)
+
             elif self.algorithm == "direct":
                 return GroupedCoefficients(
                     self.settings, (self.matrix.conj()).T @ other
                 )
-                
+
         elif isinstance(other, GC):  # `f = F*fhat`    (fhat = other)
             if self.settings != other.settings:
                 raise ValueError(
@@ -468,10 +470,10 @@ def worker(i):
                         worker(i)
 
                 return sum(results)
-            
+
             elif self.algorithm == "keops":
                 return self.transforms[0] @ other.data
-            
+
             elif self.algorithm == "direct":
                 return self.matrix @ other.data
         else:
diff --git a/src/pyGroupedTransforms/NFFTtools.py b/src/pyGroupedTransforms/NFFTtools.py
index d0b02c6..432ac47 100644
--- a/src/pyGroupedTransforms/NFFTtools.py
+++ b/src/pyGroupedTransforms/NFFTtools.py
@@ -1,11 +1,10 @@
 import numpy as np
-
-from pyGroupedTransforms import *
-
-import torch
 import pykeops
+import torch
 from pykeops.torch import LazyTensor
 
+from pyGroupedTransforms import *
+
 
 def datalength(
     bandwidths: np.ndarray,
@@ -173,6 +172,7 @@ def adjoint(f):  # function adjoint(f::Vector{ComplexF64})::Vector{ComplexF64}
         dtype=np.complex128, shape=(M, N), mfunc=trafo, rmfunc=adjoint
     )
 
+
 def get_matrix(
     bandwidths, X
 ):  # get_matrix(bandwidths::Vector{Int}, X::Array{Float64})::Array{ComplexF64}