Ast formats a Rego AST element. If the passed value is not a valid AST
element, Ast returns nil and an error. Ast relies on all AST elements having
non-nil Location values. If an AST element with a nil Location value is
encountered, a default location will be set on the AST node.
Source formats a Rego source file. The bytes provided must describe a complete
Rego module. If they don't, Source will return an error resulting from the attempt
to parse the bytes.