Reduce this array by applying `func` along some dimension(s).

        Parameters
        ----------
        func : function
            Function which can be called in the form
            `func(x, axis=axis, **kwargs)` to return the result of reducing an
            np.ndarray over an integer valued axis.
        dim : str or sequence of str, optional
            Dimension(s) over which to apply `func`.
        axis : int or sequence of int, optional
            Axis(es) over which to apply `func`. Only one of the 'dim'
            and 'axis' arguments can be supplied. If neither are supplied, then
            the reduction is calculated over the flattened array (by calling
            `func(x)` without an axis argument).
        keep_attrs : bool, optional
            If True, the variable's attributes (`attrs`) will be copied from
            the original object to the new one.  If False (default), the new
            object will be returned without attributes.
        **kwargs : dict
            Additional keyword arguments passed on to `func`.

        Returns
        -------
        reduced : Array
            Array with summarized data and the indicated dimension(s)
            removed.

def reduce(self, func, dim=None, axis=None,
               keep_attrs=None, allow_lazy=False, **kwargs):
        """Reduce this array by applying `func` along some dimension(s).

        Parameters
        ----------
        func : function
            Function which can be called in the form
            `func(x, axis=axis, **kwargs)` to return the result of reducing an
            np.ndarray over an integer valued axis.
        dim : str or sequence of str, optional
            Dimension(s) over which to apply `func`.
        axis : int or sequence of int, optional
            Axis(es) over which to apply `func`. Only one of the 'dim'
            and 'axis' arguments can be supplied. If neither are supplied, then
            the reduction is calculated over the flattened array (by calling
            `func(x)` without an axis argument).
        keep_attrs : bool, optional
            If True, the variable's attributes (`attrs`) will be copied from
            the original object to the new one.  If False (default), the new
            object will be returned without attributes.
        **kwargs : dict
            Additional keyword arguments passed on to `func`.

        Returns
        -------
        reduced : Array
            Array with summarized data and the indicated dimension(s)
            removed.
        """
        if dim is common.ALL_DIMS:
            dim = None
        if dim is not None and axis is not None:
            raise ValueError("cannot supply both 'axis' and 'dim' arguments")

        if dim is not None:
            axis = self.get_axis_num(dim)
        input_data = self.data if allow_lazy else self.values
        if axis is not None:
            data = func(input_data, axis=axis, **kwargs)
        else:
            data = func(input_data, **kwargs)

        if getattr(data, 'shape', ()) == self.shape:
            dims = self.dims
        else:
            removed_axes = (range(self.ndim) if axis is None
                            else np.atleast_1d(axis) % self.ndim)
            dims = [adim for n, adim in enumerate(self.dims)
                    if n not in removed_axes]

        if keep_attrs is None:
            keep_attrs = _get_keep_attrs(default=False)
        attrs = self._attrs if keep_attrs else None

        return Variable(dims, data, attrs=attrs)