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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 mean_hub_height(self):
 r""" Calculates the mean hub height of the wind farm. The mean hub height of a wind farm is necessary for power output calculations with an aggregated wind farm power curve containing wind turbines with different hub heights. Hub heights of wind turbines with higher nominal power weigh more than others. Assigns the hub height to the wind farm object. Returns ------- self Notes ----- The following equation is used [1]_: .. math:: h_{WF} = e^{\sum\limits_{k}{ln(h_{WT,k})} \frac{P_{N,k}}{\sum\limits_{k}{P_{N,k}}}} with: :math:`h_{WF}`: mean hub height of wind farm, :math:`h_{WT,k}`: hub height of the k-th wind turbine of a wind farm, :math:`P_{N,k}`: nominal power of the k-th wind turbine References .. [1] Knorr, K.: "Modellierung von raum-zeitlichen Eigenschaften der Windenergieeinspeisung für wetterdatenbasierte Windleistungssimulationen". Universität Kassel, Diss., 2016, p. 35 """

        self.hub_height = np.exp(
            sum(np.log(wind_dict['wind_turbine'].hub_height) *
                wind_dict['wind_turbine'].nominal_power *
                wind_dict['number_of_turbines']
                for wind_dict in self.wind_turbine_fleet) /
            self.get_installed_power())
        return self