code: def add_function_def(self, name, args, is_scalar_output):
      func_args = ", ".join(
          [
              f"{n}: {self._get_var_declare_type(is_vector)}"
              for is_vector, n in args
          ]
      )
      return_type = self._get_var_declare_type(not is_scalar_output)
      function_def = f"fn {name}({func_args}) -> {return_type} {{"
      self.add_code_line(function_def)
      self.increase_indent()
  
file_path: m2cgen/m2cgen/interpreters/rust/code_generator.py
imports: from contextlib import contextmanager
  from m2cgen.interpreters.code_generator import CLikeCodeGenerator, CodeTemplate
label_desc: Use image node_id 1 for calling the RustCodeGenerator obj's underlying member method code with example usage: obj.add_function_def(name, args, is_scalar_output) without return types