add: _format_arg override to support tr

Author: nicholsn

nipype/interfaces/fsl/utils.py

@@ -169,6 +169,13 @@ class Merge(FSLCommand):
     input_spec = MergeInputSpec
     output_spec = MergeOutputSpec
 
+    def _format_arg(self, name, spec, value):
+    if name == 'tr':
+        if self.inputs.dimension != 'tr':
+            raise ValueError('When TR is specified, dimension has to be tr')
+        return spec.argstr % value
+    return super(FSLMerge, self)._format_arg(name, spec, value)
+
 
 class ExtractROIInputSpec(FSLCommandInputSpec):
     in_file = File(exists=True, argstr="%s",