Add this DataFrame to another or a scalar/list.

        Args:
            other: What to add this this DataFrame.
            axis: The axis to apply addition over. Only applicaable to Series
                or list 'other'.
            level: A level in the multilevel axis to add over.
            fill_value: The value to fill NaN.

        Returns:
            A new DataFrame with the applied addition.

def add(self, other, axis="columns", level=None, fill_value=None):
        """Add this DataFrame to another or a scalar/list.

        Args:
            other: What to add this this DataFrame.
            axis: The axis to apply addition over. Only applicaable to Series
                or list 'other'.
            level: A level in the multilevel axis to add over.
            fill_value: The value to fill NaN.

        Returns:
            A new DataFrame with the applied addition.
        """
        return self._binary_op(
            "add", other, axis=axis, level=level, fill_value=fill_value
        )