Many times, your steam generator is hard wired which is when the electrical connection is permanent and controlled through a breaker. For units that come with a cord and plug, or if you choose to add this feature, there is a specific outlet configuration needed for each plug type. In these instances, the GFCI is generally a function of the circuit breaker rather than the outlet.
Your electrician will be able to determine the correct outlet and breaker needed and be able to address any electrical code requirements as well. To learn more about GFCIs or Ground Fault Circuit Interrupters, check out this fact sheet from the Consumer Product Safety Commission www.cpsc.gov/cpscpub/pubs/99.html