code: @Override
      public String getHeader(String name) {
          return (headers != null ? headers.getFirst(name) : null);
      }
docs: Returns the value of the response header with the given name.
  
  <p>If a response header with the given name exists and contains
  multiple values, the value that was added first will be returned.
  
  @param name the name of the response header whose value to return
  @return the value of the response header with the given name,
  or {@code null} if no header with the given name has been set
  on this response