Adjusted module docstring.

pysegcnn/preprocessing/sparcs.py

-"""Functions to preprocess the Sparcs dataset.
+"""Command line script to preprocess the Sparcs dataset.
+
+After downloading the Sparcs dataset, from the repository's root directory run:
+
+    python pysegcnn/preprocessing/sparcs.py
+
+The above command will print the usage of the script.
 
 License
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