Shift this dataset by an offset along one or more dimensions.

        Only data variables are moved; coordinates stay in place. This is
        consistent with the behavior of ``shift`` in pandas.

        Parameters
        ----------
        shifts : Mapping with the form of {dim: offset}
            Integer offset to shift along each of the given dimensions.
            Positive offsets shift to the right; negative offsets shift to the
            left.
        fill_value: scalar, optional
            Value to use for newly missing values
        **shifts_kwargs:
            The keyword arguments form of ``shifts``.
            One of shifts or shifts_kwarg must be provided.

        Returns
        -------
        shifted : Dataset
            Dataset with the same coordinates and attributes but shifted data
            variables.

        See also
        --------
        roll

        Examples
        --------

        >>> ds = xr.Dataset({'foo': ('x', list('abcde'))})
        >>> ds.shift(x=2)
        <xarray.Dataset>
        Dimensions:  (x: 5)
        Coordinates:
          * x        (x) int64 0 1 2 3 4
        Data variables:
            foo      (x) object nan nan 'a' 'b' 'c'

def shift(self, shifts=None, fill_value=dtypes.NA, **shifts_kwargs):
        """Shift this dataset by an offset along one or more dimensions.

        Only data variables are moved; coordinates stay in place. This is
        consistent with the behavior of ``shift`` in pandas.

        Parameters
        ----------
        shifts : Mapping with the form of {dim: offset}
            Integer offset to shift along each of the given dimensions.
            Positive offsets shift to the right; negative offsets shift to the
            left.
        fill_value: scalar, optional
            Value to use for newly missing values
        **shifts_kwargs:
            The keyword arguments form of ``shifts``.
            One of shifts or shifts_kwarg must be provided.

        Returns
        -------
        shifted : Dataset
            Dataset with the same coordinates and attributes but shifted data
            variables.

        See also
        --------
        roll

        Examples
        --------

        >>> ds = xr.Dataset({'foo': ('x', list('abcde'))})
        >>> ds.shift(x=2)
        <xarray.Dataset>
        Dimensions:  (x: 5)
        Coordinates:
          * x        (x) int64 0 1 2 3 4
        Data variables:
            foo      (x) object nan nan 'a' 'b' 'c'
        """
        shifts = either_dict_or_kwargs(shifts, shifts_kwargs, 'shift')
        invalid = [k for k in shifts if k not in self.dims]
        if invalid:
            raise ValueError("dimensions %r do not exist" % invalid)

        variables = OrderedDict()
        for name, var in self.variables.items():
            if name in self.data_vars:
                var_shifts = {k: v for k, v in shifts.items()
                              if k in var.dims}
                variables[name] = var.shift(
                    fill_value=fill_value, shifts=var_shifts)
            else:
                variables[name] = var

        return self._replace_vars_and_dims(variables)