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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 as_index(keys, axis=semantics.axis_default, base=False, stable=True, lex_as_struct=False):
 """ casting rules for a keys object to an index object the preferred semantics is that keys is a sequence of key objects, except when keys is an instance of tuple, in which case the zipped elements of the tuple are the key objects the axis keyword specifies the axis which enumerates the keys if axis is None, the keys array is flattened if axis is 0, the first axis enumerates the keys which of these two is the default depends on whether backwards_compatible == True if base==True, the most basic index possible is constructed. this avoids an indirect sort; if it isnt required, this has better performance """

    if isinstance(keys, Index):
        if type(keys) is BaseIndex and base==False:
            keys = keys.keys    #need to upcast to an indirectly sorted index type
        else:
            return keys         #already done here
    if isinstance(keys, tuple):
        if lex_as_struct:
            keys = as_struct_array(*keys)
        else:
            return LexIndex(keys, stable)

    try:
        keys = np.asarray(keys)
    except:
        raise TypeError('Given object does not form a valid set of keys')
    if axis is None:
        keys = keys.flatten()
    if keys.ndim==1:
        if base:
            return BaseIndex(keys)
        else:
            return Index(keys, stable=stable)
    else:
        return ObjectIndex(keys, axis, stable=stable)