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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 heatmap(z, x=None, y=None, colorscale='Viridis'):
 """Create a heatmap. Parameters z : TODO x : TODO, optional y : TODO, optional colorscale : TODO, optional Returns ------- Chart """

    z = np.atleast_1d(z)
    data = [go.Heatmap(z=z, x=x, y=y, colorscale=colorscale)]
    return Chart(data=data)