在 GraphQL 中报错：Variable “$sessionId” of type “String” used in position expecting type “String!”.

{
    "errors": [
        {
            "message": "Variable \"$sessionId\" of type \"String\" used in position expecting type \"String!\".",
            "extensions": {
                "category": "graphql"
            },
            "locations": [
                {
                    "line": 2,
                    "column": 163
                },
                {
                    "line": 8,
                    "column": 16
                }
            ]
        }
    ]
}

mutation ThemeUpdate($themeId: ID!, $settings: [ThemeSettingDataInput!], $sections: [ThemeSettingsDataSectionInput!], $appEmbeds: [ThemeSettingsDataBlockInput!], $sessionId: String) {
  onlineStoreThemeSettingsDataUpdate(
    themeId: $themeId
    settings: $settings
    sections: $sections
    appEmbeds: $appEmbeds
    sessionId: $sessionId
  ) {
    sessionId
    __typename
  }
}

mutation ThemeUpdate($themeId: ID!, $settings: [ThemeSettingDataInput!], $sections: [ThemeSettingsDataSectionInput!], $appEmbeds: [ThemeSettingsDataBlockInput!], $sessionId: String!) {
  onlineStoreThemeSettingsDataUpdate(
    themeId: $themeId
    settings: $settings
    sections: $sections
    appEmbeds: $appEmbeds
    sessionId: $sessionId
  ) {
    sessionId
    __typename
  }
}