Update README.md

hw3/README.md

@@ -302,7 +302,7 @@ Here is how we intend the `ETL` class to be used. You can create DataFrame and c
 
 For example, the add() function creates a new column with a specified value. We might want to add a new colum to represent ages:
 ```
->> etl.add(colname="age", 0)
+>> etl.add("age", 0)
 >> etl.df
   first_name last_name  age
 0        Bob   Stewart    0