Constant sppparse::MAX_SPARSE_DEPTH

pub const MAX_SPARSE_DEPTH: u32 = 100;

The max stack frames Sparse will go before returning a cyclic.

For each SparseSelector in your objects, you should count 3 stack frames.

i.e. If you have a document with a depth of 30 references. The maximum depth of the recursive function will be at most 90.