Adds TODO for CIF conversion module

Author: AndrewSazonov

src/easydiffraction/analysis/calculators/calculator_pdffit.py

@@ -46,6 +46,7 @@ def _calculate_single_model_pattern(self,
         # Set sample model parameters
         # ---------------------------
 
+        # TODO: move CIF v2 -> CIF v1 conversion to a separate module
         # Convert the sample model to CIF supported by PDFfit
         v2_cif_string = sample_model.as_cif()
         # convert to version 1 of CIF format