code: public String getHeaderValue(final String pHeaderName) {
          List<String> values = headers.get(pHeaderName);
  
          return (values != null && values.size() > 0) ? values.get(0) : null;
      }
docs: Gets the first header value set for the given header in this response.
  If the header is not set, {@code null} is returned.
  Useful for headers that don't have multiple values, like
  {@code "Content-Type"} or {@code "Content-Length"}.
  
  @param pHeaderName the header name
  @return a {@code String}, or {@code null} if there is no
  such header in this response.