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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 ustack(arrs, axis=0):
 """Join a sequence of arrays along a new axis while preserving units The axis parameter specifies the index of the new axis in the dimensions of the result. For example, if ``axis=0`` it will be the first dimension and if ``axis=-1`` it will be the last dimension. This is a wrapper around np.stack that preserves units. See the documentation for np.stack for full details. Examples -------- [[1 2 3] [2 3 4]] km """

    v = np.stack(arrs, axis=axis)
    v = _validate_numpy_wrapper_units(v, arrs)
    return v