human
I wrote the below code

    def bigrams(s):
        return set((s[i:(i + 2)] for i in xrange((len(s) - 1))))
    nx = bigrams(string1)
    ny = bigrams(string2)
    nt = nx.intersection(ny)
    return ((2.0 * len(nt)) / ((len(nx) + len(ny)) or 1))

What's a good function header?

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Here's a good function header?
assistant
#Here's a good function header.

def dice_coefficient(string1, string2):