diff --git a/iDEA/methods/hartree.py b/iDEA/methods/hartree.py
index 5360e0a..62cdb21 100644
--- a/iDEA/methods/hartree.py
+++ b/iDEA/methods/hartree.py
@@ -14,6 +14,7 @@
 
 kinetic_energy_operator = iDEA.methods.non_interacting.kinetic_energy_operator
 external_potential_operator = iDEA.methods.non_interacting.external_potential_operator
+propagate_step = iDEA.methods.non_interacting.propagate_step
 
 
 def hartree_potential_operator(s: iDEA.system.System, n: np.ndarray) -> np.ndarray:
diff --git a/iDEA/methods/hartree_fock.py b/iDEA/methods/hartree_fock.py
index 108b148..648751e 100644
--- a/iDEA/methods/hartree_fock.py
+++ b/iDEA/methods/hartree_fock.py
@@ -16,6 +16,7 @@
 kinetic_energy_operator = iDEA.methods.non_interacting.kinetic_energy_operator
 external_potential_operator = iDEA.methods.non_interacting.external_potential_operator
 hartree_potential_operator = iDEA.methods.hartree.hartree_potential_operator
+propagate_step = iDEA.methods.non_interacting.propagate_step
 
 
 def exchange_potential_operator(s: iDEA.system.System, p: np.ndarray) -> np.ndarray:
diff --git a/iDEA/methods/hybrid.py b/iDEA/methods/hybrid.py
index 1fdbbd4..ff33a87 100644
--- a/iDEA/methods/hybrid.py
+++ b/iDEA/methods/hybrid.py
@@ -21,6 +21,7 @@
 exchange_correlation_potential_operator = (
     iDEA.methods.lda.exchange_correlation_potential_operator
 )
+propagate_step = iDEA.methods.non_interacting.propagate_step
 
 
 def hamiltonian(
diff --git a/iDEA/methods/lda.py b/iDEA/methods/lda.py
index 71e948a..6147b16 100644
--- a/iDEA/methods/lda.py
+++ b/iDEA/methods/lda.py
@@ -16,6 +16,7 @@
 kinetic_energy_operator = iDEA.methods.non_interacting.kinetic_energy_operator
 external_potential_operator = iDEA.methods.non_interacting.external_potential_operator
 hartree_potential_operator = iDEA.methods.hartree.hartree_potential_operator
+propagate_step = iDEA.methods.non_interacting.propagate_step
 
 
 class HEG:
diff --git a/iDEA/methods/non_interacting.py b/iDEA/methods/non_interacting.py
index 9da0429..629b3a3 100644
--- a/iDEA/methods/non_interacting.py
+++ b/iDEA/methods/non_interacting.py
@@ -465,13 +465,13 @@ def propagate(
     Propagate a set of orbitals forward in time due to a dynamic local pertubation.
 
     | Args:
-    |    s: iDEA.system.System, System object.  
-    |    state: iDEA.state.SingleBodyState, State to be propigated. 
-    |    v_ptrb: np.ndarray, Local perturbing potential on the grid of t and x values, indexed as v_ptrb[time,space]. 
+    |    s: iDEA.system.System, System object.
+    |    state: iDEA.state.SingleBodyState, State to be propigated.
+    |    v_ptrb: np.ndarray, Local perturbing potential on the grid of t and x values, indexed as v_ptrb[time,space].
     |    t: np.ndarray, Grid of time values. \n
-    |    hamiltonian_function: Callable, Hamiltonian function [If None this will be the non_interacting function]. (default = None) 
-    |    restricted: bool, Is the calculation restricted (r) on unrestricted (u). (default=False) 
-    |    name: str, Name of method. (default = "non_interacting") 
+    |    hamiltonian_function: Callable, Hamiltonian function [If None this will be the non_interacting function]. (default = None)
+    |    restricted: bool, Is the calculation restricted (r) on unrestricted (u). (default=False)
+    |    name: str, Name of method. (default = "non_interacting")
 
     | Returns:
     |    evolution: iDEA.state.SingleBodyEvolution, Solved time-dependent evolution.
diff --git a/iDEA/observables.py b/iDEA/observables.py
index 9ef077b..6748b97 100644
--- a/iDEA/observables.py
+++ b/iDEA/observables.py
@@ -543,7 +543,9 @@ def exchange_energy(
     elif len(p.shape) == 3:
         E_x = np.zeros(shape=p.shape[0], dtype=complex)
         for j in range(E_x.shape[0]):
-            E_x[j] = 0.5 * np.tensordot(p[j, :, :].T, v_x[j, :, :], axes=2) * s.dx * s.dx
+            E_x[j] = (
+                0.5 * np.tensordot(p[j, :, :].T, v_x[j, :, :], axes=2) * s.dx * s.dx
+            )
         return E_x.real
 
     else:
diff --git a/iDEA/reverse_engineering.py b/iDEA/reverse_engineering.py
index dee3362..c4473d4 100644
--- a/iDEA/reverse_engineering.py
+++ b/iDEA/reverse_engineering.py
@@ -219,7 +219,10 @@ def reverse_propagation(
 
     # Reverse propagation.
     for j, ti in enumerate(
-        tqdm(t, desc="iDEA.reverse_engineering.reverse_propagation: reversing propagation")
+        tqdm(
+            t,
+            desc="iDEA.reverse_engineering.reverse_propagation: reversing propagation",
+        )
     ):
         if j != 0:
 
diff --git a/iDEA/state.py b/iDEA/state.py
index 5d22fb4..bdd6089 100644
--- a/iDEA/state.py
+++ b/iDEA/state.py
@@ -34,7 +34,7 @@ def __init__(
         r"""
         State of particles in a many-body state.
 
-        This is described by a spatial part 
+        This is described by a spatial part
         .. math:: \psi(x_1,x_2,\dots,x_N)
         on the spatial grid, and a spin
         part on the spin grid