lib/parse/model/associations/relation_collection_proxy.rb
def all(constraints = {})
      q = query( {limit: :max}.merge(constraints) )
      if block_given?
        # if we have a query, then use the Proc with it (more efficient)
        return q.present? ? q.results(&Proc.new) : collection.each(&Proc.new)
      end
      # if no block given, get all the results
      q.present? ? q.results : collection
    end
def all(constraints = {})
      q = query( {limit: :max}.merge(constraints) )
      if block_given?
        # if we have a query, then use the Proc with it (more efficient)
        return q.present? ? q.results(&Proc.new) : collection.each(&Proc.new)
      end
      # if no block given, get all the results
      q.present? ? q.results : collection
    end
You can get items within the collection relation filtered by a specific set
 of query constraints.