# Sage manifold error

HI, there. I tried to compute some examples with Sage manifolds and I got this:

## sage: E2 = Manifold(2, 'E^2', latex_name=r'\mathbb{E}^2',start_index=1)

NotImplementedError Traceback (most recent call last) <ipython-input-37-4b1cf0743b4e> in <module>() ----> 1 E2 = Manifold(Integer(2), 'E^2', latex_name=r'\mathbb{E}^2',start_index=Integer(1))

/usr/lib/sagemath/src/sage/misc/lazy_import.pyx in sage.misc.lazy_import.LazyImport.__call__ (/usr/lib/sagemath//src/build/cythonized/sage/misc/lazy_import.c:3627)()
384 True
385 """
--> 386 return self._get_object()(*args, **kwds)
387
388 def __repr__(self):

/usr/lib/sagemath/local/lib/python2.7/site-packages/sage/manifolds/manifold.py in Manifold(dim, name, latex_name, field, structure, start_index, **extra_kwds) 1653 else: 1654 raise NotImplementedError("manifolds of type {} are not ".format(structure) + -> 1655 "implemented") 1656 return TopologicalManifold(dim, name, field, structure, 1657 latex_name=latex_name, start_index=start_index,

NotImplementedError: manifolds of type smooth are not implemented

How could I fix it?

PS: My plan is to compute metric, connection, curvature, and riemann tensors. PS(II): Are differential forms implemented in Sage? Thanks!