How to use the pygls.types.MessageType function in pygls

async def register_completions(ls: JsonLanguageServer, *args):
    """Register completions method on the client."""
    params = RegistrationParams([Registration(str(uuid.uuid4()), COMPLETION,
                                              {"triggerCharacters": "[':']"})])
    response = await ls.register_capability_async(params)
    if response is None:
        ls.show_message('Successfully registered completions method')
    else:
        ls.show_message('Error happened during completions registration.',
                        MessageType.Error)

def parse_wdl(ls: Server, uri: str):
    ls.show_message_log('Validating ' + uri, MessageType.Info)
    diagnostics, wdl = _parse_wdl(ls, uri)
    ls.publish_diagnostics(uri, diagnostics)
    ls.show_message_log(
        '{} {}'.format('Valid' if wdl else 'Invalid', uri),
        MessageType.Info if wdl else MessageType.Warning
    )

async def unregister_completions(ls: JsonLanguageServer, *args):
    """Unregister completions method on the client."""
    params = UnregistrationParams([Unregistration(str(uuid.uuid4()), COMPLETION)])
    response = await ls.unregister_capability_async(params)
    if response is None:
        ls.show_message('Successfully unregistered completions method')
    else:
        ls.show_message('Error happened during completions unregistration.',
                        MessageType.Error)

types = _get_types(doc.children, dict())
        ls.wdl_types[uri] = types
        ls.wdl_defs[uri], ls.wdl_refs[uri] = _get_links(doc.children, types, dict(), dict())
        ls.wdl_symbols[uri] = sorted(_get_symbols(doc.children, []))

        return list(_lint_wdl(ls, doc)), doc

    except WDL.Error.MultipleValidationErrors as errs:
        return [_diagnostic_err(e) for e in errs.exceptions], None

    except WDLError as e:
        return [_diagnostic_err(e)], None

    except Exception as e:
        ls.show_message_log(str(e), MessageType.Error)
        return [], None

    def show_message(self, message, msg_type=MessageType.Info):
        """Sends message to the client to display message."""
        self.notify(WINDOW_SHOW_MESSAGE, ShowMessageParams(msg_type, message))

    def show_message(self, message, msg_type=MessageType.Info) -> None:
        """Sends message to the client to display message."""
        self.lsp.show_message(message, msg_type)

    def show_message_log(self, message, msg_type=MessageType.Log):
        """Sends message to the client's output channel."""
        self.notify(WINDOW_LOG_MESSAGE, LogMessageParams(msg_type, message))

    def show_message_log(self, message, msg_type=MessageType.Log) -> None:
        """Sends message to the client's output channel."""
        self.lsp.show_message_log(message, msg_type)

def _check_linter_available(ls: Server):
    if getattr(_check_linter_available, 'skip', False):
         return

    if not WDL.Lint._shellcheck_available:
        ls.show_message('''
            WDL task command linter is not available on the system PATH.
            Please install ShellCheck and/or add it to the PATH:
            https://github.com/koalaman/shellcheck#installing
        ''', MessageType.Warning)
    _check_linter_available.skip = True