<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def as_required_fields(self, fields=[]):
 """ set required to True """

        fields = self.filter_fields(fields)
        for f in fields:
            f = self.fields[f.name]
            f.required = True