AttributeError: 'str' object has no attribute 'copy'

[astrosumit]

Hi,
When I run the following:

import astroRMS
astroRMS.calc_rms('image.fits')

It gives the following error:
Traceback (most recent call last):
File "", line 1, in
File "/home/user/anaconda3/lib/python3.7/site-packages/astroRMS.py", line 289, in calc_rms
working_data = image_data.copy()
AttributeError: 'str' object has no attribute 'copy'