code: function deleteMany(query, callback) {
      callback = callback || emptyFn
      self.emit('deleteMany', query)
      data = Mingo.remove(data, query)
      self.emit('afterDeleteMany', query)
      callback()
    }
docs: Deletes entities based on a query. Emits a 'delete' event. Performs a find
  by query, then calls delete for each item returned. Returns an error if no
  items match the query.
  
  @param {Object} query to delete on
  @param {Function} callback (optional)
  @api public