Revert "remove sending generator"
Revert "remove sending generator"

This reverts commit f79014cbe4f2cafae5015969f68330ff258f0494.

bjodah/symengine.py,symengine/symengine.py,bjodah/symengine.py,symengine/symengine.py,symengine/symengine.py,bjodah/symengine.py