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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 velocity_dispersion(self, kwargs_lens, kwargs_lens_light, lens_light_model_bool_list=None, aniso_param=1, r_eff=None, R_slit=0.81, dR_slit=0.1, psf_fwhm=0.7, num_evaluate=1000):
 """ computes the LOS velocity dispersion of the lens within a slit of size R_slit x dR_slit and seeing psf_fwhm. The assumptions are a Hernquist light profile and the spherical power-law lens model at the first position. Further information can be found in the AnalyticKinematics() class. :param kwargs_lens: lens model parameters :param kwargs_lens_light: deflector light parameters :param aniso_param: scaled r_ani with respect to the half light radius :param r_eff: half light radius, if not provided, will be computed from the lens light model :param R_slit: width of the slit :param dR_slit: length of the slit :param psf_fwhm: full width at half maximum of the seeing condition :param num_evaluate: number of spectral rendering of the light distribution that end up on the slit :return: velocity dispersion in units [km/s] """

        gamma = kwargs_lens[0]['gamma']
        if 'center_x' in kwargs_lens_light[0]:
            center_x, center_y = kwargs_lens_light[0]['center_x'], kwargs_lens_light[0]['center_y']
        else:
            center_x, center_y = 0, 0
        if r_eff is None:
            r_eff = self.lens_analysis.half_light_radius_lens(kwargs_lens_light, center_x=center_x, center_y=center_y, model_bool_list=lens_light_model_bool_list)
        theta_E = kwargs_lens[0]['theta_E']
        r_ani = aniso_param * r_eff
        sigma2 = self.analytic_kinematics.vel_disp(gamma, theta_E, r_eff, r_ani, R_slit, dR_slit, FWHM=psf_fwhm, rendering_number=num_evaluate)
        return sigma2