'True if Delta is restricted to below fermi
Examples
>>> from sympy.functions.special.tensor_functions import KroneckerDelta
>>> from sympy import Symbol
>>> a = Symbol(\'a\', above_fermi=True)
>>> i = Symbol(\'i\', below_fermi=True)
>>> p = Symbol(\'p\')
>>> q = Symbol(\'q\')
>>> KroneckerDelta(p, i).is_only_below_fermi
True
>>> KroneckerDelta(p, q).is_only_below_fermi
False
>>> KroneckerDelta(p, a).is_only_below_fermi
False
See Also
is_above_fermi, is_below_fermi, is_only_above_fermi'

@property
def is_only_below_fermi(self):

    return ((self.args[0].assumptions0.get('below_fermi') or self.args[1].assumptions0.get('below_fermi')) or False)
