diff --git a/src/engines/core/base_worker.py b/src/engines/core/base_worker.py
index 2ca2f72..b2da574 100644
--- a/src/engines/core/base_worker.py
+++ b/src/engines/core/base_worker.py
@@ -190,7 +190,7 @@ class BaseRenderWorker(Base):
         return generated_args
 
     def get_raw_args(self):
-        raw_args_string = self.args.get('raw', None)
+        raw_args_string = self.args.get('raw', '')
         raw_args = None
         if raw_args_string:
             import shlex
diff --git a/src/engines/engine_manager.py b/src/engines/engine_manager.py
index 9721181..77018f8 100644
--- a/src/engines/engine_manager.py
+++ b/src/engines/engine_manager.py
@@ -12,6 +12,9 @@ logger = logging.getLogger()
 
 
 class EngineManager:
+    """Class that manages different versions of installed renderers and handles fetching and downloading new versions,
+    if possible.
+    """
 
     engines_path = None
     download_tasks = []
@@ -283,6 +286,17 @@ class EngineManager:
 
 
 class EngineDownloadWorker(threading.Thread):
+    """A thread worker for downloading a specific version of a rendering engine.
+
+    This class handles the process of downloading a rendering engine in a separate thread,
+    ensuring that the download process does not block the main application.
+
+    Attributes:
+        engine (str): The name of the rendering engine to download.
+        version (str): The version of the rendering engine to download.
+        system_os (str, optional): The operating system for which to download the engine. Defaults to current OS type.
+        cpu (str, optional): Requested CPU architecture. Defaults to system CPU type.
+    """
     def __init__(self, engine, version, system_os=None, cpu=None):
         super().__init__()
         self.engine = engine