fix formatting + flake8

Author: renefritze

src/pymor_dealii/pymor/operator.py

@@ -3,7 +3,6 @@
 # License: BSD 2-Clause License (http://opensource.org/licenses/BSD-2-Clause)
 
 from pymor.operators.interface import Operator
-from pymor.operators.constructions import ZeroOperator
 
 from pymor_dealii.pymor.vectorarray import DealIIVectorSpace
 import pymor_dealii_bindings as pd2
@@ -42,10 +41,17 @@ def apply_inverse(self, V, mu=None, initial_guess=None, least_squares=False):
             self.matrix.cg_solve(r.impl, v.impl)
         return R
 
-    def _assemble_lincomb(self, operators, coefficients, identity_shift=0., solver_options=None, name=None):
+    def _assemble_lincomb(
+        self,
+        operators,
+        coefficients,
+        identity_shift=0.0,
+        solver_options=None,
+        name=None,
+    ):
         if not all(isinstance(op, (DealIIMatrixOperator)) for op in operators):
             return None
-        if identity_shift != 0.:
+        if identity_shift != 0.0:
             return None
         assert not solver_options  # linear solver is not yet configurable