fix: do not accept multiple files

Author: oesteban

sdcflows/interfaces/bspline.py

@@ -276,9 +276,7 @@ def _run_interface(self, runtime):
 
 
 class _ApplyCoeffsFieldInputSpec(BaseInterfaceInputSpec):
-    in_data = InputMultiObject(
-        File(exist=True, mandatory=True, desc="input EPI data to be corrected")
-    )
+    in_data = File(exist=True, mandatory=True, desc="input EPI data to be corrected")
     in_coeff = InputMultiObject(
         File(exists=True),
         mandatory=True,
@@ -288,23 +286,17 @@ class _ApplyCoeffsFieldInputSpec(BaseInterfaceInputSpec):
         exists=True,
         desc="the transform by which the fieldmap can be resampled on the target EPI's grid.",
     )
-    in_xfms = InputMultiObject(
-        File(exists=True), desc="list of head-motion correction matrices"
-    )
-    ro_time = InputMultiObject(
-        traits.Float(mandatory=True, desc="EPI readout time (s).")
-    )
-    pe_dir = InputMultiObject(
-        traits.Enum(
-            "i",
-            "i-",
-            "j",
-            "j-",
-            "k",
-            "k-",
-            mandatory=True,
-            desc="the phase-encoding direction corresponding to in_data",
-        )
+    in_xfms = File(exists=True, desc="list of head-motion correction matrices")
+    ro_time = traits.Float(mandatory=True, desc="EPI readout time (s).")
+    pe_dir = traits.Enum(
+        "i",
+        "i-",
+        "j",
+        "j-",
+        "k",
+        "k-",
+        mandatory=True,
+        desc="the phase-encoding direction corresponding to in_data",
     )
     num_threads = traits.Int(nohash=True, desc="number of threads")
     approx = traits.Bool(
@@ -361,18 +353,6 @@ class ApplyCoeffsField(SimpleInterface):
     def _run_interface(self, runtime):
         from sdcflows.transform import B0FieldTransform
 
-        n = len(self.inputs.in_data)
-
-        ro_time = self.inputs.ro_time
-        if len(ro_time) == 1:
-            ro_time *= n
-
-        pe_dir = self.inputs.pe_dir
-        if len(pe_dir) == 1:
-            pe_dir *= n
-
-        unwarp = None
-
         # Pre-cached interpolator object
         unwarp = B0FieldTransform(coeffs=[nb.load(cname) for cname in self.inputs.in_coeff])
 
@@ -390,12 +370,12 @@ def _run_interface(self, runtime):
         # self._results["out_field"] = out_field
 
         # HMC matrices are only necessary when reslicing the data (i.e., apply())
-        hmc_mats = None
+        # Check the length of in_xfms matches that of in_data
         self._results["out_corrected"] = unwarp.apply(
             self.inputs.in_data,
-            pe_dir,
-            ro_time,
-            xfms=hmc_mats,
+            self.inputs.pe_dir,
+            self.input.ro_time,
+            xfms=self.inputs.in_xfms,
             # num_threads=(
             #     None if not isdefined(self.inputs.num_threads) else self.inputs.num_threads
             # ),