Generalized flag handling & support for flag dependent quantities

- flags can be force when setting boundaries, this is helpful for:
- setting up quantities (e.g. relaxation rate..) dependent on current
  flag configuration
- bit operation fix when pickling: function has to have the same name
  as the python object

creationfunctions.py

@@ -278,8 +278,10 @@ def create_lb_collision_rule(lb_method=None, optimization={}, **kwargs):
 
     if params['velocity_input'] is not None:
         eqs = [Assignment(cqc.zeroth_order_moment_symbol, sum(lb_method.pre_collision_pdf_symbols))]
-        velocity_field = params['velocity_input']
-        eqs += [Assignment(u_sym, velocity_field(i)) for i, u_sym in enumerate(cqc.first_order_moment_symbols)]
+        velocity_input = params['velocity_input']
+        if isinstance(velocity_input, Field):
+            velocity_input = velocity_input.center_vector
+        eqs += [Assignment(u_sym, velocity_input[i]) for i, u_sym in enumerate(cqc.first_order_moment_symbols)]
         eqs = AssignmentCollection(eqs, [])
         collision_rule = lb_method.get_collision_rule(conserved_quantity_equations=eqs)
     else:

plot2d.py

@@ -37,8 +37,8 @@ def boundary_handling(boundary_handling_obj, slice_obj=None, boundary_name_to_co
             'FixedDensity': '#009e73',
         }
 
-    boundary_names = []
-    flag_values = []
+    boundary_names = ['domain']
+    flag_values = [boundary_handling_obj.flag_interface.domain_flag]
     for boundary_obj in boundary_handling_obj.boundary_objects:
         boundary_names.append(boundary_obj.name)
         flag_values.append(boundary_handling_obj.get_flag(boundary_obj))