diff --git a/tardis/transport/montecarlo/base.py b/tardis/transport/montecarlo/base.py
index 1d4e6750ca9..6638f43e917 100644
--- a/tardis/transport/montecarlo/base.py
+++ b/tardis/transport/montecarlo/base.py
@@ -103,7 +103,6 @@ def initialize_transport_state(
         packet_collection = self.packet_source.create_packets(
             no_of_packets, seed_offset=iteration
         )
-        
 
         geometry_state = simulation_state.geometry.to_numba()
         opacity_state = opacity_state_initialize(
@@ -111,11 +110,13 @@ def initialize_transport_state(
             self.line_interaction_type,
             self.montecarlo_configuration.DISABLE_LINE_SCATTERING,
         )
-        opacity_state = opacity_state[simulation_state.geometry.v_inner_boundary_index: simulation_state.geometry.v_outer_boundary_index]
+        opacity_state = opacity_state[
+            simulation_state.geometry.v_inner_boundary_index : simulation_state.geometry.v_outer_boundary_index
+        ]
         estimators = initialize_estimator_statistics(
             opacity_state.tau_sobolev.shape, gamma_shape
         )
-        
+
         transport_state = MonteCarloTransportState(
             packet_collection,
             estimators,