code: @Pure
  	public final Transform2D toTransform2D(Segment1D<?, ?> segment) {
  		assert segment != null : AssertMessages.notNullParameter(0);
  		final Point2D<?, ?> a = segment.getFirstPoint();
  		if (a == null) {
  			return null;
  		}
  		final Point2D<?, ?> b = segment.getLastPoint();
  		if (b == null) {
  			return null;
  		}
  		return toTransform2D(a.getX(), a.getY(), b.getX(), b.getY());
  	}
docs: Replies a 2D transformation that is corresponding to this transformation.
  
  @param segment is the segment.
  @return the 2D transformation or <code>null</code> if the segment could not be mapped
  to 2D.