'Leading term as a polynomial element.
Examples
>>> from sympy.polys.rings import ring
>>> from sympy.polys.domains import ZZ
>>> _, x, y = ring(\'x, y\', ZZ)
>>> (3*x*y + y**2).leading_term()
3*x*y'

def leading_term(self):

    p = self.ring.zero
    expv = self.leading_expv()
    if (expv is not None):
        p[expv] = self[expv]
    return p
