code: public static Writable filterLine(URL self, @ClosureParams(value = SimpleType.class, options = "java.lang.String") Closure predicate) throws IOException {
          return IOGroovyMethods.filterLine(newReader(self), predicate);
      }
docs: Filter lines from a URL using a closure predicate.  The closure
  will be passed each line as a String, and it should return
  <code>true</code> if the line should be passed to the writer.
  
  @param self      a URL
  @param predicate a closure which returns boolean and takes a line
  @return a writable which writes out the filtered lines
  @throws IOException if an IO exception occurs
  @see IOGroovyMethods#filterLine(java.io.Reader, groovy.lang.Closure)
  @since 1.6.8