from aslprep.niworkflows.utils.spaces import SpatialReferences
from aslprep.workflows.asl import init_asl_std_trans_wf
wf = init_asl_std_trans_wf(
    mem_gb=3,
    omp_nthreads=1,
    spaces=SpatialReferences(
    spaces=[('MNI152Lin', {})],
    checkpoint=True))