I followed the sample code from @codeslord, but for some reason I had to access my screenshot data differently:
# Open the Firefox webdriver
driver = webdriver.Firefox()
# Find the element that you're interested in
imagepanel = driver.find_element_by_class_name("panel-height-helper")
# Access the data bytes for the web element
datatowrite = imagepanel.screenshot_as_png
# Write the byte data to a file
outfile = open("imagepanel.png", "wb")
outfile.write(datatowrite)
outfile.close()
(using Python 3.7, Selenium 3.141.0 and Mozilla Geckodriver 71.0.0.7222)