Export monad

Created by: Durman

Problem statement

https://yadi.sk/i/RRZmVlvcX2-suA

  File "\sverchok\utils\sv_IO_monad_helpers.py", line 53, in pack_monad
    v = getattr(node, prop_name)
AttributeError: 'SvGroupNodeMonad_2672554496878' object has no attribute 'float_'