Write a method called is1to1 that accepts a map whose keys and values are strings as its parameter and returns true if no two keys map to the same value. For example, {Marty=206 9024, Hawking=1234567, Smith=9490504, Newton=1234567} should return false, but {Marty=2069024, Hawking=5551234, Smith=9490504, Newton=1234567} should return true. The empty map is considered 1-to-1 and returns true.