remove unused imports and polymatrix expressions

1 files changed, 2 insertions, 6 deletions

diff --git a/polymatrix/expression/mixins/derivativeexprmixin.py b/polymatrix/expression/mixins/derivativeexprmixin.py
index 32823e5..87d5f5b 100644
--- a/polymatrix/expression/mixins/derivativeexprmixin.py
+++ b/polymatrix/expression/mixins/derivativeexprmixin.py
@@ -1,8 +1,5 @@
 
 import abc
-import collections
-import dataclasses
-import itertools
 import typing
 
 from polymatrix.polymatrix.init.initpolymatrix import init_poly_matrix
@@ -35,11 +32,10 @@ class DerivativeExprMixin(ExpressionBaseMixin):
         state: ExpressionState,
     ) -> tuple[ExpressionState, PolyMatrix]:
 
-        state, underlying = self.underlying.apply(state=state)
+        state, underlying = self.underlying.apply(state=state)        
+        state, diff_wrt_variables = get_variable_indices(state, self.variables)
 
         assert underlying.shape[1] == 1, f'{underlying.shape=}'
-        
-        state, diff_wrt_variables = get_variable_indices(state, self.variables)
 
         terms = {}