Tangent space embedding

Different connectivity measures, including tangent space measure
Fun fact: PEP8 recommands to remove spaces around operators with highest priority if you write an arithmetic operation containing several operators with different priorities.

Therefore `x = 2*2 + 3`should be preferred to `x = 2 * 2 + 3` but most of pep8 validators will consider the first expression as non compliant (I also prefer the second expression).