I have tried the following to construct an appropriate function field:
F.<a,b>=FunctionField(QQ,2)
as a result I got
TypeError: create_key() got multiple values for keyword argument 'names'
after that I looked for the documentation but only find one variable examples. I also tried a few more versions like
F.<a,b>=FunctionField(QQ,names=('a','b'))
but did not work. Thank for any advice in this direction in advance.