diff --git a/pyrelacs/dataio/nix_writer.py b/pyrelacs/dataio/nix_writer.py
index f745a25..7fa0824 100644
--- a/pyrelacs/dataio/nix_writer.py
+++ b/pyrelacs/dataio/nix_writer.py
@@ -68,6 +68,9 @@ class NixWriter:
         log.debug(f"Samples written {index}")
 
     def _write_header(self):
+        """
+        Writing the header of the nix file
+        """
         self.nix_file = nixio.File.open(path="data.nix", mode=nixio.FileMode.Overwrite)
         self.block = self.nix_file.create_block("recording", "testfile")
         self.data_array = self.block.create_data_array(