NewParseCtx creates new context for parsing and transforming a *Node (and its sub-tree) into an output record.

ValidateTransformDeclarations validates `transform_declarations` section of an omni schema and returns the `FINAL_OUTPUT` corresponding Decl.

CustomFuncDecl is the decl for a "custom_func".

Decl is the type for omni schema's `transform_declarations` declarations.

CustomParseFuncs is a map from custom_parse names to an actual custom parse functions.

CustomParseFuncType represents a custom_parse function type.