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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 check_1d(inp):
 """ Check input to be a vector. Converts lists to np.ndarray. Parameters inp : obj Input vector Returns ------- numpy.ndarray or None Input vector or None Examples -------- [0, 1, 2, 3] None """

    if isinstance(inp, list):
        return check_1d(np.array(inp))
    if isinstance(inp, np.ndarray):
        if inp.ndim == 1: # input is a vector
            return inp