Moves iterator iter to the start of the line line_number. If line_number is negative or larger than the number of lines in the buffer, moves iter to the start of the last line in the buffer.
line number (counted from 0)
See Implementation
Moves iterator iter to the start of the line line_number. If line_number is negative or larger than the number of lines in the buffer, moves iter to the start of the last line in the buffer.