code: def make_input(self):
          
          # Set the file paths.
          all_files ={"ddkfile_" + str(n + 1): ddk for n, ddk in enumerate(self.ddk_filepaths)}
          all_files.update({"wfkfile": self.wfk_filepath})
          files_nml = {"FILES": all_files}
          files= nmltostring(files_nml)
  
          # Get the input specified by the user
          user_file = nmltostring(self.input.as_dict())
  
          # Join them.
          return files + user_file
docs: Construct and write the input file of the calculation.