<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _check_object_exists(self):
 """Raise a KeyError if the scheduling object doesnt exist. Raise: KeyError, if the object doesnt exist in the database. """

        if not DB.get_keys(self.key):
            raise KeyError("Object with key '{}' not exist".format(self.key))