Simplify package dependencies by removing unnecessary imports

[NeoChaos12]

I currently use NASLib as a backend for defining my own search space for a benchmark. I noticed while sharing my code that the following imports introduce a number of dependencies that are not strictly necessary in use cases where only a subset of all the search spaces defined by NASLib are to be used. Auto-importing these search spaces enforces the constraint that the dependencies of each and every search space must be satisfied in order to use any single one of the search spaces. Is this truly necessary? For reference, I am currently using only the NASBench-201 search space.

NASLib/naslib/search_spaces/__init__.py

Lines 1 to 10 in afa98c3

 from .simple_cell.graph import SimpleCellSearchSpace 
 from .darts.graph import DartsSearchSpace 
 from .nasbench101.graph import NasBench101SearchSpace 
 from .nasbench201.graph import NasBench201SearchSpace 
 from .nasbenchnlp.graph import NasBenchNLPSearchSpace 
 from .nasbenchasr.graph import NasBenchASRSearchSpace 
 from .hierarchical.graph import HierarchicalSearchSpace 
 from .transbench101.graph import TransBench101SearchSpace 
  
 from .transbench101.api import TransNASBenchAPI 

[Georgia Channing]

Great issue. Have you had any success removing the packages and running without excess dependencies?