code: public B pathMapping(PathMapping pathMapping) {
          requireNonNull(pathMapping, "pathMapping");
          checkArgument(pathMapping.hasPathPatternOnly(),
                        "pathMapping: %s " +
                        "(expected: the path mapping which has only the path patterns as its condition)",
                        pathMapping.getClass().getSimpleName());
          pathMappings.add(pathMapping);
          return self();
      }
docs: Adds a {@link PathMapping} that this policy is supposed to be applied to.
  
  @param pathMapping the {@link PathMapping} that this policy is supposed to be applied to
  @return {@code this} to support method chaining.
  @throws IllegalArgumentException if the {@link PathMapping} has conditions beyond the path pattern,
  i.e. the {@link PathMapping} created by
  {@link PathMapping#withHttpHeaderInfo(Set, List, List)}