Slow introspection query execution for large schemas

The graphql-core `graphql_sync` function takes approximately 20x slower than a module that I wrote that solely executes the introspection query. https://github.com/kensho-technologies/graphql-compiler/blob/main/graphql_compiler/fast_introspection.py

With the graphql-core Python library, executing the default introspection query (outputted from `get_introspection_query`) on a schema of around ten thousand types with `graphql_sync` takes 26 seconds to run. Writing my own module that calls the same graphql-core Type resolvers executes the same query on the same schema in 1.37 seconds.

I'm not sure what exactly is the time sink with the graphql-core's approach, but it might have to do with the generality of `graphql_sync` and thus, computing the next field to resolve at every step, and also `graphql_sync`'s recursive nature. Interestingly, I ran the same query on the same schema using Graphql.js, and the execution took less than 2 seconds (around 1.7 seconds).

Thank you for your time and all the work to port GraphQL.js to Python!