def add_line_segments(self, vertices, close=True):
        """Add a straight line segment to each point in *vertices*.

        *vertices* must be an iterable of (x, y) pairs (2-tuples). Each x and
        y value is rounded to the nearest integer before use. The optional
        *close* parameter determines whether the resulting contour is
        *closed* or left *open*.

        Returns this |FreeformBuilder| object so it can be used in chained
        calls.
        """
        for x, y in vertices:
            self._add_line_segment(x, y)
        if close:
            self._add_close()
        return self