Create a new streaming emitter. Emitter will print to io. See Psych::Stream for an example.
# File ruby-3.1.2/ext/psych/lib/psych/streaming.rb, line 8
def new io
emitter = const_get(:Emitter).new(io)
class_loader = ClassLoader.new
ss = ScalarScanner.new class_loader
super(emitter, ss, {})
end