def validate_class_for(attribute, class_array)
    return true if class_array.include? @attributes[attribute].class
    add_error(attribute, "must be a #{class_array.join(" or ")} object (not #{@attributes[attribute].class})")
    false  
  end
def validate_class_for(attribute, class_array)
    return true if class_array.include? @attributes[attribute].class
    add_error(attribute, "must be a #{class_array.join(" or ")} object (not #{@attributes[attribute].class})")
    false  
  end
Compares the class of the attribute with the class or classes provided in the class array
 returns true if they match, otherwise adds an entry to the @errors collection, and returns false