update docs: programmatic/python

Author: Gerit Wagner

docs/source/dev_docs/packages/python.rst

@@ -21,3 +21,17 @@ Programmatic use of CoLRev in other Python applications is supported. The follow
     # Save the changes, add them to git, and create commit
     review_manager.dataset.save_records_dict(records)
     review_manager.dataset.create_commit(msg="Pre-screening (package/script X")
+
+It is also possible to use CoLRev utility methods to load and save different bibliography formats:
+
+.. code-block:: python
+
+    from pathlib import Path
+    from colrev.writer.write_utils import write_file
+    from colrev.loader.load_utils import load
+
+    records_dict = load(filename=Path("filename.bib"))
+
+    # modify records_dict
+
+    write_file(records_dict=records_dict, filename=Path("filename.bib"))