Mat: Namespace Poppler not available

I've installed MAT: Metadata Anonymisation Toolkit . When I tried to run mat, I got following error: user@user ~ $ mat Traceback (most recent call last): File "/usr/bin/mat", line 10, in from libmat import mat File "/usr/lib/python2.7/dist-packages/libmat/mat.py", line 22, in import strippers # this is loaded here because we need LOGGING_LEVEL File "/usr/lib/python2.7/dist-packages/libmat/strippers.py", line 9, in import office File "/usr/lib/python2.7/dist-packages/libmat/office.py", line 15, in gi.require_version('Poppler', '0.18') File "/usr/lib/python2.7/dist-packages/gi/__init__.py", line 102, in require_version raise ValueError('Namespace %s not available' % namespace) ValueError: Namespace Poppler not available I don't know how to fix this. Help. Information about my system: user@user ~ $ uname -a Linux user 4.13.0-38-generic #43~16.04.1-Ubuntu SMP Wed Mar 14 17:48:43 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux