numpy.isnan(x, /, out=None, *, where=True, casting='same_kind', order='K', dtype=None, subok=True[, signature, extobj])
x : array_like
out : ndarray, None, or tuple of ndarray and None, optional
A location into which the result is stored. If provided, it must have a shape that the inputs broadcast to. If not provided or None, a freshly-allocated array is returned. A tuple (possible only as a keyword argument) must have length equal to the number of outputs.
where : array_like, optional
At locations where the condition is True, the out array will be set to the ufunc result.
Elsewhere, the out array will retain its original value.
y : ndarray or bool
True where x is NaN, false otherwise. This is a scalar if x is a scalar.