Better comments for raw format (#494)

* Update raw.py

Improve comments

* Update raw.py

Reduce line length to within limit

* Update raw.py

Ensure the first line ends with a period (flake8)

* Update raw.py

remove white space for indent on otherwise empty line

cgt_calc/parsers/raw.py

@@ -1,4 +1,4 @@
-"""Charles Schwab parser."""
+"""Raw transaction parser."""
 
 from __future__ import annotations
 
@@ -22,10 +22,16 @@ def action_from_str(label: str) -> ActionType:
 
 class RawTransaction(BrokerTransaction):
     """
-    Represent single raw transaction.
+    Represents a single raw transaction.
 
-    Expected format is:
-    date (YYYY-MM-DD);action;symbol?;quantity;price;fees;currency
+    Example format:
+    2023-02-09,DIVIDEND,OPRA,4200,0.80,0.0,USD
+    2022-11-14,SELL,META,19,116.00,0.05,USD
+    2022-08-15,BUY,META,105,180.50,0.00,USD
+    2022-07-26,DIVIDEND,OTGLY,305,0.031737,0.0,USD
+    2022-06-06,STOCK_SPLIT,AMZN,209,0.00,0.00,USD
+
+    See tests/test_data/raw/test_data.csv for a sample file showing the expected format.
     """
 
     def __init__(