[Impl] parallel composition

[DrCatman]

requires:

• [ ] #56
• [ ] #57
• [ ] #59
• [ ] lists of blocks

[mzargham]

annotations

def parallel(blocks: List[Block])-> Block:

api

from cadcad.compose import parallel

myblock = parallel([block1, block2])

asserts

block1.domain == block2.domain

expects

myblock.domain ==  block1.domain
myblock.domain ==  block2.domain
myblock.codomain == spaces.product([block1.codomain, block2.codomain])