[ModelicaSystem] add missing docstrings

Author: syntron

OMPython/ModelicaSystem.py

@@ -303,6 +303,10 @@ def parse_simflags(simflags: str) -> dict[str, Optional[str | dict[str, str]]]:
 
 
 class ModelicaSystem:
+    """
+    Class to run OpenModelica simulations.
+    """
+
     def __init__(
             self,
             fileName: Optional[str | os.PathLike | pathlib.Path] = None,
@@ -472,6 +476,9 @@ def setTempDirectory(self, customBuildDirectory: Optional[str | os.PathLike | pa
         return tempdir
 
     def getWorkDirectory(self) -> OMCPath:
+        """
+        Get the defined working directory of the ModelicaSystem instance.
+        """
         return self._tempdir
 
     def buildModel(self, variableFilter: Optional[str] = None):