Single JavaScript expression. The following functions and objects are available:

• {'results.'}: the result of step at id 'id' (use {'results?.'} if id may not exist because branch was not chosen)
• flow_input: the object containing the flow input arguments
• previous_result: the result of previous step
• params: the object containing the current step static values
• variable(path): the function returning the variable (including secrets) at given path as a string
• resource(path): the function returning the resource at a given path as an object

If using multiple statements, the last statement shall finish with a return. e.g: `return x`