of unmasked values
    before trimming, the number of values after trimming is
    ``(1 - proportiontocut) * n``.  Default is 0.2.
tail : {'left','right'}, optional
    If 'left' the `proportiontocut` lowest values will be masked.
    If 'right' the `proportiontocut` highest values will be masked.
    Default is 'left'.
inclusive : {(bool, bool) tuple}, optional
    Tuple indicating whether the number of data being masked on each side
    should be rounded (True) or truncated (False).  Default is
    (True, True).
axis : int, optional
    Axis along which to perform the trimming.
    If None, the input array is first flattened.  Default is None.

Returns
-------
trimtail : ndarray
    Returned array of same shape as `data` with masked tail values.

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