<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_feature_penalty(self):
 """Get the feature penalty of the Dataset. Returns ------- feature_penalty : numpy array or None Feature penalty for each feature in the Dataset. """

        if self.feature_penalty is None:
            self.feature_penalty = self.get_field('feature_penalty')
        return self.feature_penalty