'Extract attributes from the element based on rules provided in the
mapping dictionary.
:param   response: The JSON response to parse the values from.
:type    response: ``dict``
:param   mapping: Dictionary with the extra layout
:type    mapping: ``dict``
:rtype:  ``dict``'

@staticmethod
def _get_extra_dict(response, mapping):

    extra = {}
    for (attribute, values) in mapping.items():
        transform_func = values['transform_func']
        value = response.get(values['key_name'])
        extra[attribute] = (transform_func(value) if value else None)
    return extra
