Add docstring to MAI labs formatter

TTS/tts/datasets/formatters.py

@@ -60,7 +60,13 @@ def mozilla_de(root_path, meta_file):
 
 
 def mailabs(root_path, meta_files=None):
-    """Normalizes M-AI-Labs meta data files to TTS format"""
+    """Normalizes M-AI-Labs meta data files to TTS format
+    
+    Args:
+        root_path (str): root folder of the MAILAB language folder. 
+        meta_files (str):  list of meta files to be used in the training. If None, finds all the csv files
+            recursively. Defaults to None
+    """
     speaker_regex = re.compile("by_book/(male|female)/(?P<speaker_name>[^/]+)/")
     if meta_files is None:
         csv_files = glob(root_path + "/**/metadata.csv", recursive=True)