code: def has_attr(cls, attr_name):
      
      if attr_name in cls.attrs:
        return True
  
      if isinstance(cls.primary_key_name, str) and cls.primary_key_name == attr_name:
        return True
  
      if isinstance(cls.primary_key_name, tuple) and attr_name in cls.primary_key_name:
        return True
  
      if cls.timestamps is not None and attr_name in cls.timestamps:
        return True
  
      return False
docs: Check to see if an attribute is defined for the model.