comp map

gistfile1.py

    def add_map(self, input_, zorder=None, alpha=1, levels=False):
        """Adds a map to the CompositeMap
        
        Parameters
        ----------
        input_ : {sunpy.map, string}
            Map instance or filepath to map to be added
        zorder : int
            The index to use when determining where the map should lie along
            the z-axis; maps with higher z-orders appear above maps with lower
            z-orders.
        alpha : float
            Opacity at which the map should be displayed. An alpha value of 0
            results in a fully transparent image while an alpha value of 1
            results in a fully opaque image. Values between result in semi-
            transparent images.

        """
        if zorder is None:
            zorder = max([m.zorder for m in self._maps]) + 10
        
        m = Map(input_)
        assert isinstance(Map, GenericMap)
        m.zorder = zorder
        m.alpha = alpha
        m.levels = levels
        
        self._maps.append(m)

Easy fix: add_map should take an already instantiated map, rather than a file name. Done.