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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 add_densities(density1, density2):
 """ Method to sum two densities. Args: density1: First density. density2: Second density. Returns: Dict of {spin: density}. """

    return {spin: np.array(density1[spin]) + np.array(density2[spin])
            for spin in density1.keys()}