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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 angle(v1, v2):
 """Return the angle in radians between vectors 'v1' and 'v2'."""

    v1_u = unit_vector(v1)
    v2_u = unit_vector(v2)
    return np.arccos(np.clip(np.dot(v1_u, v2_u), -1.0, 1.0))