Io.Backendval make_context : Shared_ast.decl_ctx -> backend_contextval print_encoding : vc_encoding -> stringval solve_vc_encoding : backend_context -> vc_encoding -> solver_resultval print_model : backend_context -> model -> stringval is_model_empty : model -> boolval translate_expr : 
  backend_context ->
  Shared_ast.typed Dcalc.Ast.expr ->
  backend_context * vc_encodingval encode_asserts : 
  backend_context ->
  Shared_ast.typed Dcalc.Ast.expr ->
  backend_context