This code defines two functions, bm_1 and bm_2, which are used to generate and plot Brownian motion samples. The generate_brownian_motion function is a helper function that generates a single Brownian motion sample. It takes two arguments, simulation_time and num_timesteps, which represent the total time of the simulation and the number of timesteps to split the simulation time into, respectively. First, the function calculates the variance of the noise at each timestep by dividing the simulation_time by the num_timesteps. It then generates num_timesteps random normal samples with the calculated variance. Next, it sets the first element of the noise array to 0 and calculates the Brownian motion by summing the noise cumulatively. Finally, it returns the calculated Brownian motion. The bm_2 function generates and plots multiple Brownian motion samples. It takes three arguments: num_samples (the number of Brownian motion samples to generate), simulation_time (the total time of the simulation), and num_timesteps (the number of timesteps to split the simulation time into). First, the function initializes the minimum and maximum values of the Brownian motion to very large/small values. It then generates num_samples Brownian motion samples using the generate_brownian_motion function. For each sample, it generates an array of equally spaced values from 0 to simulation_time. It then plots the Brownian motion and updates the minimum and maximum values if necessary. After generating and plotting all of the samples, the function generates a caption for the plot with the minimum and maximum values of the Brownian motion and sets the title and labels for the plot. Finally, it saves the plot to a file and displays it on the screen. The bm_1 function is similar to bm_2, but it generates and plots only a single Brownian motion sample. It takes no arguments and sets the simulation time and number of timesteps to default values. It then generates a Brownian motion sample using the generate_brownian_motion function, generates an array of equally spaced values from 0 to the simulation time, calculates the minimum and maximum values of the Brownian motion, plots the Brownian motion, generates a caption for the plot with the minimum and maximum values of the Brownian motion, sets the title and labels for the plot, saves the plot to a file, and displays it on the screen. At the end of the code calls the bm_1 and bm_2 functions to generate and plot the Brownian motion samples.