Takes a text fragment from the content of "From" starting at "Start" and ending at "End".
- If "End" is omitted all of the content from "Start" on is taken.
- If "Start" and/or "End" are negative, then these positions are counted from the end of the content of "From" in stead of from the front.
- The text to take a text fragment from.
- The starting position of the text fragment.
- End (optional)
- The ending position of the text fragment.