headers: RawAxiosResponseHeaders | AxiosResponseHeaders;

AxiosResponse<any, any>.headers: AxiosResponseHeaders | Partial<RawAxiosHeaders & {
    Server: AxiosHeaderValue;
    "Content-Type": AxiosHeaderValue;
    "Content-Length": AxiosHeaderValue;
    "Cache-Control": AxiosHeaderValue;
    "Content-Encoding": AxiosHeaderValue;
} & {
    ...;
}>

  // `headers` the HTTP headers that the server responded with
  // All header names are lower cased and can be accessed using the bracket notation.
  // Example: `response.headers['content-type']`
  headers: {},

const response = await axios.head(url);
// typed as any, but has a value
const lowercase = response.headers['content-length'];
// correctly typed, but has an undefined value
const titlecase = response.headers['Content-Length'];