def is_numpy(array):
    """Return True if array is a numpy array

    Parameters
    ----------
    array : array-like
       array is either a numpy array, a masked array, a dask array or a xarray.

    Returns
    -------
    test : bool
    """
    test =  bool( isinstance(array,np.ndarray)
                  + isinstance(array,np.ma.masked_array) )
    return test