code: function(block){
      if (this.pp) this.buf.push("pug_indent.push('" + Array(this.indents + 1).join(this.pp) + "');");
      this.buf.push('block && block();');
      if (this.pp) this.buf.push("pug_indent.pop();");
    }
docs: Visit a mixin's `block` keyword.
  
  @param {MixinBlock} block
  @api public