code: public ObjectSchema withProperty(PropertySchema schema) {
  		_properties = _properties != null ? _properties : new ArrayList<PropertySchema>();
  		_properties.add(schema);
  		return this;
  	}
docs: Adds a validation schema for an object property.
  
  This method returns reference to this exception to implement Builder pattern
  to chain additional calls.
  
  @param schema a property validation schema to be added.
  @return this validation schema.
  
  @see PropertySchema