code: def add_constant(self, stream, value):
          
  
          if stream in self.constant_database:
              raise ArgumentError("Attempted to set the same constant twice", stream=stream, old_value=self.constant_database[stream], new_value=value)
  
          self.constant_database[stream] = value
docs: Store a constant value for use in this sensor graph.
  
          Constant assignments occur after all sensor graph nodes have been
          allocated since they must be propogated to all appropriate virtual
          stream walkers.
  
          Args:
              stream (DataStream): The constant stream to assign the value to
              value (int): The value to assign.