def key(name, strategy, operator, additional = nil, &block)
      ::Symbol.add_key(name, strategy, operator, additional, &block)
    end
def key(name, strategy, operator, additional = nil, &block)
      ::Symbol.add_key(name, strategy, operator, additional, &block)
    end
Adds a method on Symbol for convenience in where queries for the
 provided operators.

 @example Add a symbol key.
   key :all, "$all

 @param [ Symbol ] name The name of the method.
 @param [ Symbol ] strategy The merge strategy.
 @param [ String ] operator The MongoDB operator.
 @param [ String ] additional The additional MongoDB operator.

 @since 1.0.0