own method has_key for class Hash. -howto

Dear all,

Can you help me how can I implement my own "has_key" method for "hash class."

class Hash

        def my_each_key(&block)
                self.each { |key|
                yield(key[0])
                }
        end
       
        def my_each_value(&block)
                self.each { |value|
                yield(value[1])
                }
        end

        def has_key()
                #todo
        end

end

h = {1 => 1.0, 2 => 2.0, 3 => 3.0 }

many thanks in advance,

salai.