rust-index: handle `MixedIndex` in `pyindex_to_graph`
On the long run we will want to implement the Graph trait directly in Rust, but
for now we take the path with the least amount of change to focus on the coming
persistent NodeMap code.
We test this new code through with the lazy ancestors code.
Differential Revision: https://phab.mercurial-scm.org/D7657
{
// Enforcing
"eqeqeq" : true, // true: Require triple equals (===) for comparison
"forin" : true, // true: Require filtering for..in loops with obj.hasOwnProperty()
"freeze" : true, // true: prohibits overwriting prototypes of native objects such as Array, Date etc.
"nonbsp" : true, // true: Prohibit "non-breaking whitespace" characters.
"undef" : true, // true: Require all non-global variables to be declared (prevents global leaks)
// Environments
"browser" : true // Web Browser (window, document, etc)
}