code: function(hasStatements) {
      if (this.hasStatements_ === hasStatements) {
        return;
      }
      if (hasStatements) {
        this.appendStatementInput('STACK')
            .appendField(Blockly.Msg.PROCEDURES_DEFNORETURN_DO);
        if (this.getInput('RETURN')) {
          this.moveInputBefore('STACK', 'RETURN');
        }
      } else {
        this.removeInput('STACK', true);
      }
      this.hasStatements_ = hasStatements;
    }
docs: Add or remove the statement block from this function definition.
  @param {boolean} hasStatements True if a statement block is needed.
  @this Blockly.Block