svd_bank.py: add documentation

gstlal-inspiral/python/svd_bank.py

@@ -16,6 +16,7 @@
 # 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 
 ## @file
+# The module to implement SVD decomposition of CBC waveforms
 #
 # ### Review Status
 #