diff --git a/b_asic/GUI/drag_button.py b/b_asic/GUI/drag_button.py
index cb6a9ca0a32b8a1bb149c8f8a887fc32e491434c..36d03c0796c3139db13f6a5b15e0abb6f71238d0 100644
--- a/b_asic/GUI/drag_button.py
+++ b/b_asic/GUI/drag_button.py
@@ -19,6 +19,8 @@ from b_asic.operation import Operation
 from b_asic.port import InputPort
 
 if TYPE_CHECKING:
+    from qtpy.QtWidgets import QGraphicsTextItem
+
     from b_asic.GUI.main_window import SFGMainWindow
 
 
@@ -90,13 +92,13 @@ class DragButton(QPushButton):
         """Return the type name of the underlying operation."""
         return self.operation.type_name()
 
-    def add_label(self, label: str) -> None:
+    def add_label(self, label: "QGraphicsTextItem") -> None:
         """
         Add label to button.
 
         Parameters
         ----------
-        label : src
+        label : QGraphicsTextItem
             The label to add.
         """
         self.label = label
diff --git a/b_asic/resources.py b/b_asic/resources.py
index 41dcac6bf30cbbf2fa7e5a6cf7b5773459f79553..1fad9dbaabb7aa1e611b81ecacb7c854e303ab4c 100644
--- a/b_asic/resources.py
+++ b/b_asic/resources.py
@@ -3,7 +3,7 @@ import re
 from collections import Counter, defaultdict
 from functools import reduce
 from math import log2
-from typing import Dict, Iterable, List, Optional, Tuple, TypeVar, Union
+from typing import Dict, Iterable, List, Literal, Optional, Tuple, TypeVar, Union
 
 import matplotlib.pyplot as plt
 import networkx as nx
@@ -864,7 +864,7 @@ class ProcessCollection:
 
     def split_on_execution_time(
         self,
-        heuristic: str = "left_edge",
+        heuristic: Literal["graph_color", "left_edge"] = "left_edge",
         coloring_strategy: str = "saturation_largest_first",
     ) -> List["ProcessCollection"]:
         """
diff --git a/b_asic/schedule.py b/b_asic/schedule.py
index 8365d194b1dc39afdc2713d5c84b3d6f1ee72fad..54066e2e73a64c9766d3c3f714dcfe6fcaf73a98 100644
--- a/b_asic/schedule.py
+++ b/b_asic/schedule.py
@@ -7,7 +7,7 @@ Contains the schedule class for scheduling operations in an SFG.
 import io
 import sys
 from collections import defaultdict
-from typing import Dict, List, Optional, Sequence, Tuple, cast
+from typing import Dict, List, Literal, Optional, Sequence, Tuple, cast
 
 import matplotlib.pyplot as plt
 import numpy as np
@@ -100,7 +100,7 @@ class Schedule:
         sfg: SFG,
         schedule_time: Optional[int] = None,
         cyclic: bool = False,
-        algorithm: str = "ASAP",
+        algorithm: Literal["ASAP", "ALAP", "provided"] = "ASAP",
         start_times: Optional[Dict[GraphID, int]] = None,
         laps: Optional[Dict[GraphID, int]] = None,
         max_resources: Optional[Dict[TypeName, int]] = None,
diff --git a/b_asic/scheduler_gui/main_window.py b/b_asic/scheduler_gui/main_window.py
index b331abcc35e48620e427096a70a4d5959fa72156..7a0c41147385419af5af61a34ee7ef9f333b68fc 100644
--- a/b_asic/scheduler_gui/main_window.py
+++ b/b_asic/scheduler_gui/main_window.py
@@ -14,7 +14,7 @@ import webbrowser
 from collections import defaultdict, deque
 from copy import deepcopy
 from importlib.machinery import SourceFileLoader
-from typing import TYPE_CHECKING, Deque, List, Optional, cast
+from typing import TYPE_CHECKING, Deque, List, Optional, cast, overload
 
 # Qt/qtpy
 import qtpy
@@ -1006,6 +1006,18 @@ class ScheduleMainWindow(QMainWindow, Ui_MainWindow):
             self.actionToggle_full_screen.setIcon(get_icon('full-screen-exit'))
 
 
+@overload
+def start_scheduler(schedule: Schedule) -> Schedule: ...
+
+
+@overload
+def start_scheduler(schedule: None) -> Optional[Schedule]: ...
+
+
+@overload
+def start_scheduler() -> Optional[Schedule]: ...
+
+
 def start_scheduler(schedule: Optional[Schedule] = None) -> Optional[Schedule]:
     """
     Start scheduler GUI.