'Increment or decrement a key by a provided delta.
Args:
key: Key to increment or decrement. If an iterable collection, each
one of the keys will be offset.
is_negative: Boolean, if this is a decrement.
delta: Non-negative integer amount (int or long) to increment
or decrement by.
namespace: a string specifying an optional namespace to use in
the request.
initial_value: initial value to put in the cache, if it doesn\'t
already exist.  The default value, None, will not create a cache
entry if it doesn\'t already exist.
Returns:
New long integer value, or None on cache miss or network/RPC/server
error.
Raises:
ValueError: If delta is negative.
TypeError: If delta isn\'t an int or long.'

def _incrdecr(self, key, is_negative, delta, namespace=None, initial_value=None):

    rpc = self._incrdecr_async(key, is_negative, delta, namespace, initial_value)
    return rpc.get_result()
