 Complete the following phrase:  Krejčíková is a Grand Slam champion, having won the 2021 French Open singles title, the womens doubles titles at the 2018 French Open, 2018 Wimbledon and 2021 French Open and the mixed doubles titles at the Australian Open in 2019, 2020, and 2021. Krejčíková also won an Olympic gold medal in womens doubles alongside Kateřina Siniaková at the 