Fill missing values in this object.

        This operation follows the normal broadcasting and alignment rules that
        xarray uses for binary arithmetic, except the result is aligned to this
        object (``join='left'``) instead of aligned to the intersection of
        index coordinates (``join='inner'``).

        Parameters
        ----------
        value : scalar, ndarray, DataArray, dict or Dataset
            Used to fill all matching missing values in this dataset's data
            variables. Scalars, ndarrays or DataArrays arguments are used to
            fill all data with aligned coordinates (for DataArrays).
            Dictionaries or datasets match data variables and then align
            coordinates if necessary.

        Returns
        -------
        Dataset

def fillna(self, value):
        """Fill missing values in this object.

        This operation follows the normal broadcasting and alignment rules that
        xarray uses for binary arithmetic, except the result is aligned to this
        object (``join='left'``) instead of aligned to the intersection of
        index coordinates (``join='inner'``).

        Parameters
        ----------
        value : scalar, ndarray, DataArray, dict or Dataset
            Used to fill all matching missing values in this dataset's data
            variables. Scalars, ndarrays or DataArrays arguments are used to
            fill all data with aligned coordinates (for DataArrays).
            Dictionaries or datasets match data variables and then align
            coordinates if necessary.

        Returns
        -------
        Dataset
        """
        if utils.is_dict_like(value):
            value_keys = getattr(value, 'data_vars', value).keys()
            if not set(value_keys) <= set(self.data_vars.keys()):
                raise ValueError('all variables in the argument to `fillna` '
                                 'must be contained in the original dataset')
        out = ops.fillna(self, value)
        return out