'Figure' object has no attribute 'add_gridspec'

This error occurs when you try to use the `add_gridspec` function on a `Figure` object in Matplotlib that does not support this function. This function was added in Matplotlib version 3.4, so if you are using an earlier version of Matplotlib, you will not be able to use this function.

To avoid this error, you can either upgrade to the latest version of Matplotlib, or use a different method for creating a grid of subplots on your figure. One alternative method is to use the `subplots` function, which allows you to specify the number of rows and columns in the grid, and returns an array of axes objects that you can use to plot your data.

Here is an example of using the `subplots` function to create a 2x2 grid of subplots:

import matplotlib.pyplot as plt

fig, axs = plt.subplots(nrows=2, ncols=2)
axs[0, 0].plot([1, 2, 3], [4, 5, 6])
axs[0, 1].scatter([1, 2, 3], [4, 5, 6])
axs[1, 0].bar([1, 2, 3], [4, 5, 6])
axs[1, 1].hist([1, 2, 3, 3, 3, 3, 3, 3, 3, 3])

plt.show()

This code creates a 2x2 grid of subplots and plots some data on each of them using the `plot`, `scatter`, `bar`, and `hist` functions. The resulting figure should display the subplots arranged in a 2x2 grid.