docs: public String getHeaderField(int pIndex) {
          // TODO: getInputStream() first, to make sure we have header fields
          if (pIndex >= responseHeaders.length) {
              return null;
          }
          String field = responseHeaders[pIndex];
  
          // pIndex == 0, means the response code etc (i.e. "HTTP/1.1 200 OK").
          if ((pIndex == 0) || (field == null)) {
              return field;
          }
          int idx = field.indexOf(':');
  
          return ((idx > 0)
                  ? field.substring(idx).trim()
                  : "");  // TODO: ""  or null?
      }