diff --git a/cura/CuraApplication.py b/cura/CuraApplication.py
index e9ed1bf978..d479b0fe18 100755
--- a/cura/CuraApplication.py
+++ b/cura/CuraApplication.py
@@ -15,7 +15,7 @@ from PyQt5.QtQml import qmlRegisterUncreatableType, qmlRegisterSingletonType, qm
 
 from UM.i18n import i18nCatalog
 from UM.Application import Application
-from UM.Decorators import override, deprecated
+from UM.Decorators import override
 from UM.FlameProfiler import pyqtSlot
 from UM.Logger import Logger
 from UM.Message import Message
@@ -1870,16 +1870,14 @@ class CuraApplication(QtApplication):
         main_window = QtApplication.getInstance().getMainWindow()
         if main_window:
             return main_window.width()
-        else:
-            return 0
+        return 0
 
     @pyqtSlot(result = int)
     def appHeight(self) -> int:
         main_window = QtApplication.getInstance().getMainWindow()
         if main_window:
             return main_window.height()
-        else:
-            return 0
+        return 0
 
     @pyqtSlot()
     def deleteAll(self, only_selectable: bool = True) -> None:
diff --git a/cura/LayerData.py b/cura/LayerData.py
index 796e71cbdc..72824591ab 100644
--- a/cura/LayerData.py
+++ b/cura/LayerData.py
@@ -16,8 +16,7 @@ class LayerData(MeshData):
     def getLayer(self, layer):
         if layer in self._layers:
             return self._layers[layer]
-        else:
-            return None
+        return None
 
     def getLayers(self):
         return self._layers
diff --git a/cura/LayerPolygon.py b/cura/LayerPolygon.py
index ca752e35ee..353d195100 100644
--- a/cura/LayerPolygon.py
+++ b/cura/LayerPolygon.py
@@ -61,7 +61,7 @@ class LayerPolygon:
         
         # When type is used as index returns true if type == LayerPolygon.InfillType or type == LayerPolygon.SkinType or type == LayerPolygon.SupportInfillType
         # Should be generated in better way, not hardcoded.
-        self._isInfillOrSkinTypeMap = numpy.array([0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0], dtype = numpy.bool)
+        self._is_infill_or_skin_type_map = numpy.array([0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0], dtype = numpy.bool)
         
         self._build_cache_line_mesh_mask = None  # type: Optional[numpy.ndarray]
         self._build_cache_needed_points = None  # type: Optional[numpy.ndarray]
@@ -153,7 +153,7 @@ class LayerPolygon:
         return self._color_map[line_types]
 
     def isInfillOrSkinType(self, line_types: numpy.ndarray) -> numpy.ndarray:
-        return self._isInfillOrSkinTypeMap[line_types]
+        return self._is_infill_or_skin_type_map[line_types]
 
     def lineMeshVertexCount(self) -> int:
         return self._vertex_end - self._vertex_begin
diff --git a/cura/PrintJobPreviewImageProvider.py b/cura/PrintJobPreviewImageProvider.py
index a8df5aa273..8b46c6db37 100644
--- a/cura/PrintJobPreviewImageProvider.py
+++ b/cura/PrintJobPreviewImageProvider.py
@@ -3,6 +3,7 @@ from PyQt5.QtQuick import QQuickImageProvider
 from PyQt5.QtCore import QSize
 
 from UM.Application import Application
+from typing import Tuple
 
 
 class PrintJobPreviewImageProvider(QQuickImageProvider):
@@ -10,7 +11,7 @@ class PrintJobPreviewImageProvider(QQuickImageProvider):
         super().__init__(QQuickImageProvider.Image)
 
     ##  Request a new image.
-    def requestImage(self, id: str, size: QSize) -> QImage:
+    def requestImage(self, id: str, size: QSize) -> Tuple[QImage, QSize]:
         # The id will have an uuid and an increment separated by a slash. As we don't care about the value of the
         # increment, we need to strip that first.
         uuid = id[id.find("/") + 1:]
@@ -22,6 +23,6 @@ class PrintJobPreviewImageProvider(QQuickImageProvider):
                 if print_job.key == uuid:
                     if print_job.getPreviewImage():
                         return print_job.getPreviewImage(), QSize(15, 15)
-                    else:
-                        return QImage(), QSize(15, 15)
-        return QImage(), QSize(15,15)
\ No newline at end of file
+
+                    return QImage(), QSize(15, 15)
+        return QImage(), QSize(15, 15)
\ No newline at end of file