Docstring for some params

Author: mariosasko

src/datasets/arrow_dataset.py

@@ -952,6 +952,8 @@ def from_generator(
         Args:
             generator (:obj:`Callable`): A callable object that returns an object that supports the `iter()` protocol.
             features (:class:`Features`, optional): Dataset features.
+            cache_dir (:obj:`str`, optional, default ``"~/.cache/huggingface/datasets"``): Directory to cache data.
+            keep_in_memory (:obj:`bool`, default ``False``): Whether to copy the data in-memory.
             gen_kwargs(:obj:`dict`, optional): Keyword arguments to be passed to the `generator` callable.
 
         Returns: