'Returns the state index related to this operator.
>>> from sympy import Symbol
>>> from sympy.physics.secondquant import F, Fd, B, Bd
>>> p = Symbol(\'p\')
>>> F(p).state
p
>>> Fd(p).state
p
>>> B(p).state
p
>>> Bd(p).state
p'

@property
def state(self):

    return self.args[0]
