'Returns ``True`` if ``f`` is linear in all its variables.
Examples
>>> from sympy import Poly
>>> from sympy.abc import x, y
>>> Poly(x + y + 2, x, y).is_linear
True
>>> Poly(x*y + 2, x, y).is_linear
False'

@property
def is_linear(f):

    return f.rep.is_linear
