IPython InteractiveShell fails to yield rich output when using `%matplotlib inline`

I am writing a custom client (a web-based graph representation of an IPython Notebook) for an IPython application and the easiest way to manage IPython programmatically seems to be using the IPython.core.InteractiveShell instance.

Consider this example: when a Jupyter Notebook cell that uses rich output is executed with inline magic, Notebook shows the appropriate rich representation (a plotted image) of plt.show() inline:

%matplotlib inline
import matplotlib.pyplot as plt
import numpy as np
t = np.arange(0.0, 2.0, 0.01)
s = np.sin(2*np.pi*t)
plt.plot(t, s)
plt.xlabel('time (s)')
plt.ylabel('voltage (mV)')
plt.title('About as simple as it gets, folks')
plt.grid(True)
plt.show()

I want to be able to retrieve the image when using IPython programmatically via its API, namely InteractiveShell, like this:

from IPython.core.interactiveshell import InteractiveShell
shell = InteractiveShell()
result = shell.run_cell("...above code of the cell here...")
# result either gives an error when using %matplotlib inline or retrieves
# no useful info if no line magic is present

Problem is that InteractiveShell instance will not accept the %matplotlib inline magic, giving a NotImplementedError in its enable_gui method which is, wll, not implemented. I found very few information about this apart from a single issue on IPython's Github.

I know I can do this manually by using plt.save() but that doesn't seem right to me as I don't want to write manual interpretations each time I need another rich representation of the result. I feel like I'm missing a lot here in the way IPython works, so I'm asking for help in retrieving the results. What exactly does Jupyter Notebook do to retrieve the rich representation and perhaps can it be done painlessly via other means? I'm looking at using jupyter_client but for now that seems to be even more confusing.

UPDATE:

The io.capture_output context manager seems to be the way to go but I've been able to capture string outputs only (pretty much the same as using %%capture cell magic):

with io.capture_output() as captured:
    result = shell.run_cell(cell)
#captures strings only:

captured.stdout = {str} '<matplotlib.figure.Figure at 0x4f486d8>'