added a docstring to forward_internal

Signed-off-by: Rauf <rnasretdinov@nvidia.com>

Author: nasretdinovr

nemo/collections/audio/parts/submodules/conformer_unet.py

@@ -104,6 +104,15 @@ def forward_internal(
         cache_last_channel_len=None,
         bypass_pre_encode=None,
     ):
+        """
+        Forward pass for the ConformerEncoderUNet model with U-Net-style skip connections.
+
+        This method processes the input audio signal through the Conformer layers with optional
+        caching and U-Net-style skip connections.
+
+        Main Changes Compared to Original Conformer:
+        - Incorporates U-Net-style skip connections between encoder layers.
+        """
         if length is None:
             length = audio_signal.new_full(
                 (audio_signal.size(0),), audio_signal.size(-1), dtype=torch.int64, device=audio_signal.device