'Get streamlines by building trajectory set.'

def get_streamlines(self):

    for indent in range((self.density // 2)):
        for xi in range((self.density - (2 * indent))):
            self.traj((xi + indent), indent)
            self.traj((xi + indent), ((self.density - 1) - indent))
            self.traj(indent, (xi + indent))
            self.traj(((self.density - 1) - indent), (xi + indent))
    self.st_x = [((np.array(t[0]) * self.delta_x) + self.x[0]) for t in self.trajectories]
    self.st_y = [((np.array(t[1]) * self.delta_y) + self.y[0]) for t in self.trajectories]
    for index in range(len(self.st_x)):
        self.st_x[index] = self.st_x[index].tolist()
        self.st_x[index].append(np.nan)
    for index in range(len(self.st_y)):
        self.st_y[index] = self.st_y[index].tolist()
        self.st_y[index].append(np.nan)
