Fixing generated filename in calc step

preprocessor/preprocessor/steps/calc.py

@@ -17,7 +17,7 @@ logger = logging.getLogger(__name__)
 def calc_step(source_dir: os.PathLike, target_dir: os.PathLike, formulas: List[dict]):
     for i, item in enumerate(formulas):
         # get first filename as a base
-        filename = glob(join(source_dir, list(item['inputs'].values())[0]['glob']))
+        filename = glob(join(source_dir, list(item['inputs'].values())[0]['glob']))[0]
         target_filename = join(
             target_dir,
             replace_ext(basename(filename), item.get('output_postfix', '_proc%d' % i) + '.tif', False)