'Returns True if `o` is coplanar with self, else False.
Examples
>>> from sympy import Plane, Point3D
>>> o = (0, 0, 0)
>>> p = Plane(o, (1, 1, 1))
>>> p2 = Plane(o, (2, 2, 2))
>>> p == p2
False
>>> p.is_coplanar(p2)
True'

def is_coplanar(self, o):

    if isinstance(o, Plane):
        (x, y, z) = map(Dummy, 'xyz')
        return (not cancel((self.equation(x, y, z) / o.equation(x, y, z))).has(x, y, z))
    if isinstance(o, Point3D):
        return (o in self)
    elif isinstance(o, LinearEntity3D):
        return all(((i in self) for i in self))
    elif isinstance(o, GeometryEntity):
        return all(((i == 0) for i in self.normal_vector[:2]))
