Fix typing errors

[volcan01010]

Summary

As an ETL Helper user, I want to fix the typing errors that I get when I use ETL Helper, so that I can use type hints to help me.

Description

There are two scenarios where Pylance (the Python type checker in VS Code) marks a typing error in code that uses ETL Helper:

def select_names(conn: sqlite3.Connection) -> list[str]:
    return list(row["name"] for row in etl.iter_rows("SELECT name FROM my_table", conn))

Pylance complains with:

• "__getitem__" method not defined on type "Row" (Pylance reportIndexIssue)
• Argument of type "Connection" cannot be assigned to parameter "conn" of type "Connection" in function "iter_rows"
  "Connection" is incompatible with protocol "Connection"
  "cursor" is an incompatible type
  No overloaded function matches type "() -> None" (Pylance reportArgumentType)

It should be possible to update the type hints with ETLHelper so that these errors are not thrown.

Acceptance criteria

• Error on connection type is resolved
• Error on row type is resolved