def src_suffixes(self, env):
        """
        Returns the list of source suffixes for all src_builders of this
        Builder.

        This is essentially a recursive descent of the src_builder "tree."
        (This value isn't cached because there may be changes in a
        src_builder many levels deep that we can't see.)
        """
        sdict = {}
        suffixes = self.subst_src_suffixes(env)
        for s in suffixes:
            sdict[s] = 1
        for builder in self.get_src_builders(env):
            for s in builder.src_suffixes(env):
                if s not in sdict:
                    sdict[s] = 1
                    suffixes.append(s)
        return suffixes
Returns the list of source suffixes for all src_builders of this
        Builder.

        This is essentially a recursive descent of the src_builder "tree."
        (This value isn't cached because there may be changes in a
        src_builder many levels deep that we can't see.)