'For the given xblock, return a dict for the field\'s current state:
\'default_value\': what json\'d value will take effect if field is unset: either the field default or
inherited value,
\'explicitly_set\': boolean for whether the current value is set v default/inherited,
:param xblock:
:param field:'

def get_field_provenance(self, xblock, field):

    result = {}
    result['explicitly_set'] = xblock._field_data.has(xblock, field.name)
    try:
        result['default_value'] = xblock._field_data.default(xblock, field.name)
    except KeyError:
        result['default_value'] = field.to_json(field.default)
    return result
