title: meteor autoform: how to ignore simple schema key during insert or update
body: <p>I have following simple schema keys:</p>
  
  <pre><code>isParent: {
      type: String
     ,optional: true        
     ,custom: function(){
          if(  !this.isSet ){
              console.log('IsParent value: ',this.field.value);
              return 'required';
          }
     }
  },
  parentId: {
      type: Number
     ,optional: true
     ,custom: function(){
  
          if( (this.field('isParent').value === 'false') &amp;&amp; !this.isSet ){
  
              console.log(this.field('isParent').value);
              console.log('ParentId value: ', this.value);
              return 'required';
          }            
      }
  </code></pre>
  
  <p>I don't want to insert/update 'isParent' key in db. I only want to use it as trigger point to enable/disable the 'parentId' key in html form and in schema.</p>
  
  <p>If I don't use 'isParent' key in insert process, then meteor error is generated.</p>
  
  <p>Can some one guide me how to ignore insertion or updation of 'isParent' key during validation upon insert or update.   </p>