<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def convert(self, value, view):
 """Check that the value is an int or a float. """

        if isinstance(value, NUMERIC_TYPES):
            return value
        else:
            self.fail(
                u'must be numeric, not {0}'.format(type(value).__name__),
                view,
                True
            )