Add type signatures for slurm initializer (#1423)
Add type signatures for slurm initializer (#1423)

This is part of long running issue #873 to add type signatures to user facing code.

This PR also forces mem_per_node to be an integer, because slurm cannot deal with fractions in this field - see issue #1416
Parsl/parsl,Parsl/parsl,Parsl/parsl,Parsl/parsl