code: public B removeAttributes(String... keys) {
          for (String key : keys) {
              this.data.remove(key);
          }
          return (B) this;
      }
docs: Removes an entry of a certain keys. This can be useful, when a context is initialized with another
  existing context, but only subset of the entries should be visible. For example {@code removeAttributes
  ("a", "b", "c")} removes all attributes named 'a','b' and 'c'.
  
  @param keys the keys
  @return this Builder, for chaining