def _make_axes_dict(self, axes):
if type(axes) is dict:<EOL><INDENT>axdict = axes<EOL><DEDENT>elif type(axes) is Axis:<EOL><INDENT>ax = axes<EOL>axdict = {ax.axis_type: ax}<EOL><DEDENT>elif axes is None:<EOL><INDENT>axdict = {'<STR_LIT>': None}<EOL><DEDENT>else:<EOL><INDENT>raise ValueError('<STR_LIT>')<EOL><DEDENT>return axdict<EOL>
Makes an axes dictionary.

        .. note::

            In case the input is ``None``, the dictionary :code:`{'empty': None}`
            is returned.

        **Function-call argument** \n

        :param axes:    axes input
        :type axes:     dict or single instance of
                        :class:`~climlab.domain.axis.Axis` object or ``None``
        :raises: :exc:`ValueError`  if input is not an instance of Axis class
                                    or a dictionary of Axis objetcs
        :returns: dictionary of input axes
        :rtype: dict