title: "Item" schema is not found even i required that model.(mongoose,Node.js)
body: <p>I am trying to run hook of 'remove' in label schema.<strong><em>"Item.find is not a function"</em></strong> this is the error which I got.
  But 'Item' schema is not found.This "<strong>require</strong>"  works fine on other models.Here it is not working.</p>
  
  <p>That error  might be occurs in <code>var Item = require('./Item');</code></p>
  
  <p>This is "<strong>Label</strong>" schema.</p>
  
  <pre><code>  var mongoose = require('mongoose');
      var Schema = mongoose.Schema;
      var Item = require('./Item');
      var List = require('./List');
  
      // created schema for Item
      var labelSchema = new Schema({
        label_title: {type: String},
        color_id:{type: String, required: true},
        created_at: Date,
        updated_at: Date,
        marked : { Boolean ,default:false },
        _board: {type: Schema.Types.ObjectId, ref:'Board'}
      });
  
      //-----------------Hook--
      labelSchema.post('remove',function(doc,next){
  
        Label.remove({_id:this._id}).then(function(data){
          console.log("successfuly removed label");
        }).catch(function(error){console.log(error);
        })
  
      //-----remove label from all items
         // console.log("ITEM", Item);
          Item.find({},function(error,items){
            items.forEach(function(item){
              Item.findByIdAndUpdate(item._id,
                { "$pullAll": { "label" : [{ "label_id" : this._id }]} },function(error,result){
                  if(result)console.log("successfully removed");
                  else console.log("not removed");
                })
            })
      })
      });
  
  
      var Label = mongoose.model('Label', labelSchema);
      module.exports = Label;
  </code></pre>
  
  <p>What should I do?</p>