Update docstrings.

haystack/components/preprocessors/document_splitter.py

@@ -53,7 +53,7 @@ def run(self, documents: List[Document]):
 
  :returns: A dictionary with the following key:
  - `documents`: List of documents with the split texts. A metadata field "source_id" is added to each
- document to keep track of the original document that was split. Other metadata are copied from the original
+ document to keep track of the original document that was split. Another metadata field "page_number" is added to each number to keep track of the page it belonged to in the original document. Other metadata are copied from the original
  document.
 
  :raises TypeError: if the input is not a list of Documents.