code: public M remove(String... attrs) {
  		if (attrs != null)
  			for (String a : attrs) {
  				this.attrs.remove(a);
  				this._getModifyFlag().remove(a);
  			}
  		return (M)this;
  	}
docs: Remove attributes of this model.
  @param attrs the attribute names of the model
  @return this model