Add documentation

DataHandler.py

 from abc import ABC
 
 class DataHandler(ABC):
+    '''Defines variables that are needed for any type of interaction with FastF1's data. Any class utilizing FastF1
+    data in any way should be a subclass of the DataHandler class to inherit these variables.'''
 
     def __init__(self):
         self.numberOfDrivers = 20
         self.invalidDriverId = "NO_DRIVER"
         self.activateDebugOvertakeAnalysis = False
-        self.slickCompounds = ('SOFT', 'MEDIUM', 'HARD')
+        self.slickCompounds = ("SOFT", "MEDIUM", "HARD")
         self.validSessionTypes = ("Practice", "Qualifying", "Race")
         self.countOutPitstops = True
         self.firstFastF1Year: int = 2018
 
 class SessionIdentifier:
+    '''Uniquely identifies a single session without having to load or create the Session object'''
+
     year: int
     event: int | str
     sessionType: str
@@ -23,6 +27,10 @@ class SessionIdentifier:
 
 
 class WeatherChangeWindow:
+    '''Identifies a window of laps, during which a weather change took place. A WeatherChangeWindow is itself not
+    associated with a SessionObject or a SessionIdentifier. This association must be made and maintained by whatever
+    object or function is using an object of this class.'''
+
     firstLap: int
     lastLap: int