def METHOD_NAME(self, validated_data, instance=None):
    # Extract users' profiles
    _user_profiles = {}
    for _key, _value in validated_data.items():
        if _key in ("owner", "poc", "metadata_owner"):
            _user_profiles[_key] = _value
    for _key, _value in _user_profiles.items():
        validated_data.pop(_key)
        _u = get_user_model().objects.filter(username=_value).first()
        if _u:
            validated_data[_key] = _u
        else:
            raise InvalidGeoAppException(f"The specified '{_key}' does not exist!")
    return validated_data