you want
function test_function_2(n::Integer; num_flips=1000, T::Type{TT} = Int64) where TT
# use TT here, DO NOT USE T
end
you want
function test_function_2(n::Integer; num_flips=1000, T::Type{TT} = Int64) where TT
# use TT here, DO NOT USE T
end