'Set a single value on Validated instance.
This method should be overridded by sub-classes.
This method can only be used to assign validated attributes/items.
Args:
key: The name of the attributes
value: The value to set
Raises:
ValidationError: when no validated attribute exists on class.'

def Set(self, key, value):

    raise NotImplementedError('Subclasses    of    ValidatedBase    must    override    Set.')
