def METHOD_NAME(self):
    r"""
    Return the base space of this category.
    EXAMPLES::
        sage: M = Manifold(2, 'M', structure='top')
        sage: from sage.categories.vector_bundles import VectorBundles
        sage: VectorBundles(M, RR).base_space()
        2-dimensional topological manifold M
    """
    return self._base_space