Extract internals from a ParametricFunction object?

Questions
1

If I create a ParametricFunction object for doing ParametricIPOPTMinimize, how can extract the variables from the object?

2

If pfun is the ParametricFunction, try

Part[pfun["Creator"], 1, 2]
3

Thanks

In[21]:= cptest = 
 createParam[x^2 - y^2, {Cos[x - y] >= 0.5}, {{x, -5, 5}, {y, -5, 5}}]

Out[21]= ParametricFunction[ <> ]

In[22]:= Part[cptest["Creator"], 1, 2]

Out[22]= {x, y}