core.operators: remove Sequence? restriction on push
core.operators: remove Sequence? restriction on push

Because OutputStream is not a Sequence, and OutputStream needs push.
Probably we need something like Pushable.

iamrekcah/clay,mario-campos/clay,jckarter/clay,jckarter/clay,jckarter/clay,mario-campos/clay,iamrekcah/clay,iamrekcah/clay,mario-campos/clay,jckarter/clay,iamrekcah/clay,mario-campos/clay,jckarter/clay,jckarter/clay,iamrekcah/clay,mario-campos/clay