@classmethod<EOL><INDENT>def _convert_to_number_format(cls, number_format_dict):<DEDENT>
return number_format_dict['<STR_LIT>']<EOL>
Convert ``number_format_dict`` to an openpyxl v2.1.0 number format
initializer.
Parameters
----------
number_format_dict : dict
    A dict with zero or more of the following keys.
        'format_code' : str
Returns
-------
number_format : str