**Rust -> JSON**.
Parse a Rust source file into a `syn_serde::File` and print out a JSON
representation of the syntax tree.
**JSON -> Rust**.
Parse a JSON file into a `syn_serde::File` and print out a Rust syntax tree.
**Rust -> Pickle**
Parse a Rust source file into a `syn_serde::File` and print out a Pickle
representation of the syntax tree.