'Is this geometrical entity similar to another geometrical entity?
Two entities are similar if a uniform scaling (enlarging or
shrinking) of one of the entities will allow one to obtain the other.
Notes
This method is not intended to be used directly but rather
through the `are_similar` function found in util.py.
An entity is not required to implement this method.
If two different types of entities can be similar, it is only
required that one of them be able to determine this.
See Also
scale'

def is_similar(self, other):

    raise NotImplementedError()
