Checks floating point data columns for nans, and replaces these with
        the generic Stata for missing value (.)

def _replace_nans(self, data):
        # return data
        """Checks floating point data columns for nans, and replaces these with
        the generic Stata for missing value (.)"""
        for c in data:
            dtype = data[c].dtype
            if dtype in (np.float32, np.float64):
                if dtype == np.float32:
                    replacement = self.MISSING_VALUES['f']
                else:
                    replacement = self.MISSING_VALUES['d']
                data[c] = data[c].fillna(replacement)

        return data