Repository: ManimCommunity/manim
File: manim/mobject/coordinate_systems.py (Python)

Code before:
            The first (i.e the non-faded lines parallel to `axis_parallel_to`) and second (i.e the faded lines parallel to `axis_parallel_to`) sets of lines, respectively.
        """

        line = Line(axis_parallel_to.get_start(), axis_parallel_to.get_end())
        if ratio_faded_lines == 0:  # don't show faded lines
            ratio_faded_lines = 1  # i.e. set ratio to 1
        step = (1 / ratio_faded_lines) * freq
        lines1 = VGroup()
        lines2 = VGroup()
        unit_vector_axis_perp_to = axis_perpendicular_to.get_unit_vector()
        ranges = (
            np.arange(0, axis_perpendicular_to.x_max, step),
            np.arange(0, axis_perpendicular_to.x_min, -step),
        )
        for inputs in ranges:
            for k, x in enumerate(inputs):
                new_line = line.copy()
                new_line.shift(unit_vector_axis_perp_to * x)
                if k % ratio_faded_lines == 0:
                    lines1.add(new_line)
                else:
                    lines2.add(new_line)
        return lines1, lines2

    def get_center_point(self) -> np.ndarray:
        """Gets the center point from coordinates.

        Returns
        -------
        np.ndarray
            Returns the center point.
        """
        return self.coords_to_point(0, 0)

    def get_x_unit_size(self):
        # not yet implemented ?
        return self.get_x_axis().get_unit_size()

    def get_y_unit_size(self):
        # not yet implemented ?
        return self.get_x_axis().get_unit_size()

    def get_axes(self) -> VGroup:
        """Gets the pair of axes.

        Returns
        -------
        :class:`~.VGroup`
            Returns axes.
        """
        return self.axes

Review comment (suggestion):
I'm not sure what are the coordinates you mentioned here. It just returns the origin of the coordinate system 
```suggestion
        """Gets the origin of ``NumberPlane``.
```

Code after:
    ) -> VGroup:
        """Creates two lines representing `dx` and `df`, the labels for `dx` and `df`, and
         the secant to the curve at a particular x-value.

        Parameters
        ----------
        x
            The x-value at which the secant intersects the graph for the first time.

        graph
            The curve for which the secant will be found.

        dx
            The change in `x` after which the secant exits.

        dx_line_color
            The color of the line that indicates the change in `x`.

        dy_line_color
            The color of the line that indicates the change in `y`. Defaults to the color of :attr:`graph`.

        dx_label
            The label for the `dx` line.

        dy_label
            The label for the `dy` line.

        include_secant_line
            Whether or not to include the secant line in the graph,
            or just have the df and dx lines and labels.

        secant_line_color
            The color of the secant line.

        secant_line_length
            The length of the secant line.

        Returns
        -------
        :class:`~.VGroup`
            A group containing the elements: `dx_line`, `df_line`, and
            if applicable also :attr:`dx_label`, :attr:`df_label`, `secant_line`.

        """
        group = VGroup()

        dx = dx or float(self.x_range[1] - self.x_range[0]) / 10
        dx_line_color = dx_line_color
        dy_line_color = dy_line_color or graph.get_color()

        p1 = self.input_to_graph_point(x, graph)