Fix flake8 violations

Signed-off-by: Loy van Beek <loy.vanbeek@mojin-robotics.de>

ros1_bridge/__init__.py

@@ -797,9 +797,11 @@ def determine_field_mapping(ros1_msg, ros2_msg, mapping_rules, msg_idx):
  update_ros1_field_information(ros1_field, ros1_msg.package_name)
  mapping.add_field_pair(ros1_field, ros2_member)
  break
-
- ros1_fields_mapped_to_a_ros2_member = [field[0].name for field in mapping.fields_1_to_2.keys()]
- if not ros1_field.name in ros1_fields_mapped_to_a_ros2_member:
+
+ ros1_fields_mapped_to_a_ros2_member = [field[0].name
+ for field
+ in mapping.fields_1_to_2.keys()]
+ if ros1_field.name not in ros1_fields_mapped_to_a_ros2_member:
  # this allows fields to exist in ROS 1 but not in ROS 2
  ros1_fields_not_mapped += [ros1_field]