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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _index(array, item, key=None):
 """ Array search function. Written, because ``.index()`` method for array doesn't have `key` parameter and raises `ValueError`, if the item is not found. Args: array (list):
 List of items, which will be searched. item (whatever):
 Item, which will be matched to elements in `array`. key (function, default None):
 Function, which will be used for lookup into each element in `array`. Return: Index of `item` in `array`, if the `item` is in `array`, else `-1`. """

    for i, el in enumerate(array):
        resolved_el = key(el) if key else el

        if resolved_el == item:
            return i

    return -1