@property<EOL><INDENT>def direct_normal_radiation(self):<DEDENT>
return self._get_data_by_field(<NUM_LIT>)<EOL>
Return annual Direct Normal Radiation as a Ladybug Data Collection.

        This is the Direct Normal Radiation in Wh/m2. (Amount of solar radiation in
        Wh/m2 received directly from the solar disk on a surface perpendicular to the
        sun's rays, during the number of minutes preceding the time indicated.) If the
        field is missing ( >= 9999) or invalid ( < 0), it is set to 0. Counts of such
        missing values are totaled and presented at the end of the runperiod.
        Read more at: https://energyplus.net/sites/all/modules/custom/nrel_custom/pdfs
            /pdfs_v8.4.0/AuxiliaryPrograms.pdf (Chapter 2.9.1)