code: def addContext(self, layer, hiddenLayerName = 'hidden', verbosity = 0):
          
          # better not add context layer first if using sweep() without mapInput
          SRN.add(self, layer, verbosity)
          if hiddenLayerName in self.contextLayers:
              raise KeyError('There is already a context layer associated with this hidden layer.', \
                               hiddenLayerName)
          else:
              self.contextLayers[hiddenLayerName] = layer
              layer.kind = 'Context'
docs: Adds a context layer. Necessary to keep self.contextLayers dictionary up to date.