diff --git a/diffeopt/cometric/laplace.py b/diffeopt/cometric/laplace.py
index 6d04974..5a48e5c 100644
--- a/diffeopt/cometric/laplace.py
+++ b/diffeopt/cometric/laplace.py
@@ -1,7 +1,7 @@
 import numpy as np
 import torch
 
-def get_fourier_cometric(group, s):
+def get_fourier_cometric(group: "BaseDiffeoGroup", s: int):
     shape = group.shape
     idx, idy = group.get_raw_identity()
     lap = 4. - 2.*(torch.cos(2.*torch.pi*idx/shape[0]) + torch.cos(2.*torch.pi*idy/shape[1]))
@@ -11,9 +11,9 @@ def get_fourier_cometric(group, s):
     lapinv[0,0] = 1.
     return lapinv
 
-def get_laplace_cometric(group, s=1):
-    def cometric(momentum):
+def get_laplace_cometric(group: "BaseDiffeoGroup", s:int=1):
     lapinv = get_fourier_cometric(group, s)
+    def cometric(momentum: torch.Tensor) -> torch.Tensor:
         fx = torch.fft.fftn(momentum[0])
         fy = torch.fft.fftn(momentum[1])
         fx *= lapinv
diff --git a/diffeopt/utils.py b/diffeopt/utils.py
index 6b1f61e..bc50e0c 100644
--- a/diffeopt/utils.py
+++ b/diffeopt/utils.py
@@ -18,7 +18,7 @@ def normalize(I):
 
 from diffeopt.cometric import laplace
 
-def get_random_diffeo(group, nb_steps=10, scale=1.):
+def get_random_diffeo(group: "BaseDiffeoGroup", nb_steps:int=10, scale:float=1.) -> torch.Tensor:
     cometric = laplace.get_laplace_cometric(group, s=2)
     rm = torch.randn(*group.zero().shape)
     rv = cometric(rm)