diff --git a/mlair/helpers/filter.py b/mlair/helpers/filter.py
index 2231fcd25afdc70669b473d4d7be6fef4e66b4f1..b25d6ee10f89bfa49c2147d1758a2d24b8e7687e 100644
--- a/mlair/helpers/filter.py
+++ b/mlair/helpers/filter.py
@@ -188,10 +188,6 @@ class ClimateFIRFilter(FIRFilter):
             values (default None). Must either be a dictionary with keys available in var_dim or a single value that is
             applied to all data.
         """
-        #todo add extend_length_opts
-        # adjust all parts of code marked as todos
-        # think about different behaviour when using different extend_length_opts (is this part of dh?)
-
         self._apriori = apriori
         self.apriori_type = apriori_type
         self.apriori_diurnal = apriori_diurnal
@@ -260,7 +256,7 @@ class ClimateFIRFilter(FIRFilter):
                 input_data = self._shift_data(input_data, coord_range, self.time_dim, new_dim) - fi
 
             # create new apriori information for next iteration if no further apriori is provided
-            if len(apriori_list) < len(self.order):  #TODO: is this true? or should it be < i+1 resp. <= i
+            if len(apriori_list) < len(self.order):
                 logging.info(f"{self.station_name}: create diurnal_anomalies")
                 if self.apriori_diurnal is True and sampling == "1H":
                     diurnal_anomalies = self.create_seasonal_hourly_mean(input_data.sel({new_dim: 0}, drop=True),
@@ -631,16 +627,17 @@ class ClimateFIRFilter(FIRFilter):
     def _trim_data_to_minimum_length(data: xr.DataArray, extend_length_history: int, dim: str,
                                      minimum_length: int = None, extend_length_opts: int = 0) -> xr.DataArray:
         """
-        Trim data along given axis between either -minimum_length (if given) or -extend_length_history and 0.
+        Trim data along given axis between either -minimum_length (if given) or -extend_length_history and
+        extend_length_opts (which is default set to 0).
 
         :param data: data to trim
         :param extend_length_history: start number for trim range (transformed to negative), only used if parameter
             minimum_length is not provided
         :param dim: dim to apply trim on
         :param minimum_length: start number for trim range (transformed to negative), preferably used (default None)
+        :param extend_length_opts: number to use in "future"
         :returns: trimmed data
         """
-        #todo update doc strings
         if minimum_length is None:
             return data.sel({dim: slice(-extend_length_history, extend_length_opts)}, drop=True)
         else:
@@ -750,7 +747,7 @@ class ClimateFIRFilter(FIRFilter):
 
         # concat all variables
         logging.debug(f"{station_name}: concat all variables")
-        res = xr.concat(coll, var_dim)  #todo does this works with different extend_length_opts (is data trimmed or filled with nans, 2nd is target)
+        res = xr.concat(coll, var_dim)
 
         # create result array with same shape like input data, gaps are filled by nans
         res_full = self._create_full_filter_result_array(data, res, new_dim, station_name)