Parameters
    ----------
    arr_or_dtype : array-like or dtype
        The array or dtype to check.

    Returns
    -------
    boolean
        Whether or not the array or dtype is of the timedelta64[ns] dtype.

    Examples
    --------
    >>> from pandas.core.dtypes.common import is_timedelta64_ns_dtype
    >>> is_timedelta64_ns_dtype(np.dtype('m8[ns]'))
    True
    >>> is_timedelta64_ns_dtype(np.dtype('m8[ps]'))  # Wrong frequency
    False
    >>> is_timedelta64_ns_dtype(np.array([1, 2], dtype='m8[ns]'))
    True
    >>> is_timedelta64_ns_dtype(np.array([1, 2], dtype=np.timedelta64))
    False
    c