Add Importer.fields_active() convenience method

rattail/importing/importers.py

@@ -94,6 +94,16 @@ class Importer(object):
             self.model_name = self.model_class.__name__
         self._setup(**kwargs)
 
+    def fields_active(self, fields):
+        """
+        Convenience method to check if any of the given fields are currently
+        "active" for the importer.  Returns ``True`` or ``False``.
+        """
+        for field in fields:
+            if field in self.fields:
+                return True
+        return False
+
     def _setup(self, **kwargs):
         self.create = kwargs.pop('create', self.allow_create) and self.allow_create
         self.update = kwargs.pop('update', self.allow_update) and self.allow_update