Caps.toString_

Converts caps to a string representation. This string representation can be converted back to a #GstCaps by [gst.caps.Caps.fromString].

For debugging purposes its easier to do something like this:

`` C GST_LOG ("caps are %" GST_PTR_FORMAT, caps); ``

This prints the caps in human readable form.

The implementation of serialization up to 1.20 would lead to unexpected results when there were nested #GstCaps / #GstStructure deeper than one level.