enh: catch up with the new asyncio implementation

mriqc/workflows/functional/base.py

@@ -586,12 +586,16 @@ def hmc(name='fMRI_HMC', omp_nthreads=None):
 
     # Apply transforms to other echos
     apply_hmc = pe.MapNode(
-        niu.Function(function=_apply_transforms, input_names=['in_file', 'in_xfm']),
+        niu.Function(
+            function=_apply_transforms,
+            input_names=['in_file', 'in_xfm', 'max_concurrent'],
+        ),
         name='apply_hmc',
         iterfield=['in_file'],
         # NiTransforms is a memory hog, so ensure only one process is running at a time
         n_procs=config.environment.cpu_count,
     )
+    apply_hmc.inputs.max_concurrent = 4
 
     # fmt: off
     workflow.connect([
@@ -815,7 +819,7 @@ def _parse_tout(in_file):
     return data.mean()
 
 
-def _apply_transforms(in_file, in_xfm):
+def _apply_transforms(in_file, in_xfm, max_concurrent):
     from pathlib import Path
 
     from nitransforms.linear import load
@@ -828,6 +832,7 @@ def _apply_transforms(in_file, in_xfm):
         in_file,
         dtype_width=4,
         serialize_nvols=2,
+        max_concurrent=max_concurrent,
     )
     out_file = derive_bids_fname(
         in_file,