Type Relations
**************

All relations implement two methods ``is_relation`` and ``transform``. ``is_relation`` is
responsible for testing the validity of a relation while ``transform`` applies whatever
transformation is required to map between the types defined on the relation.

Going back to our integer example.

.. code-block:: python

    >>> import visions as v
    >>> v.Integer.relations
    [IdentityRelation(Generic -> Integer),
     InferenceRelation(Float -> Integer),
     InferenceRelation(String -> Integer)]

Now imagine a series of floats like ``[1.0, 2.0, 3.0]``.

.. code-block:: python

    >>> float_int_relation = v.Integer.relations[v.Float]
    >>> series = pd.Series([1.0, 2.0, 3.0])

    >>> series in v.Integer
    False

    >>> float_int_relation.is_relation(series)
    True

Not yet an integer, but it can be mapped to one!

.. code-block:: python

    >>> transformed_series = float_int_relation.transform(series)

    >>> transformed_series in v.Integer
    True

... and the ``transform`` method is how.

The relations between types represent the invisible bonds between types which allow
visions to map between them.