def evaluate(relation, param)
      if splat_param?
        relation.send(name, *format_param(param))
      else
        relation.send(name, format_param(param))
      end
    end
def evaluate(relation, param)
      if splat_param?
        relation.send(name, *format_param(param))
      else
        relation.send(name, format_param(param))
      end
    end
Evaluate the method in the context of the supplied relation and parameter