def METHOD_NAME(self):
    if is_msvc(self):
        raise ConanInvalidConfiguration("libverto does not support Visual Studio")
    if self.settings.os == "Windows" and self.options.shared:
        raise ConanInvalidConfiguration("Shared libraries are not supported on Windows")
    if not self._backend_dict[str(self.options.default)]:
        raise ConanInvalidConfiguration(f"Default backend({self.options.default}) must be available")
    count = lambda iterable: sum(1 if it else 0 for it in iterable)
    count_builtins = count(str(opt) == "builtin" for opt in self._backend_dict.values())
    count_externals = count(str(opt) == "external" for opt in self._backend_dict.values())
    if count_builtins > 1:
        raise ConanInvalidConfiguration("Cannot have more then one builtin backend")
    if not self.options.shared:
        if count_externals > 0:
            raise ConanInvalidConfiguration("Cannot have an external backend when building a static libverto")
    if count_builtins > 0 and count_externals > 0:
        raise ConanInvalidConfiguration("Cannot combine builtin and external backends")
    if self.options.with_tevent:
        # FIXME: missing tevent recipe
        raise ConanInvalidConfiguration("tevent is not (yet) available on conan-center")