The construct seems to be defined as:

``` multi_line_raw_string_literal : raw_string_literal_delimiter whitespace* new_line (raw_content | new_line)* new_line whitespace* raw_string_literal_delimiter ; ```

Which I think says that the opening and closing new lines (after and before the """'s) are NOT part of the content of the string literal, but new lines between them can be part of the string literal.