gst_parse_errors: no element filesrc?

[pisymbol .]

Traceback (most recent call last):
  File "./ear_height", line 224, in on_play_button_clicked
    play_widget = GstWidget(pipeline)
  File "./ear_height", line 45, in __init__
    self.bin = Gst.parse_bin_from_description(pipeline, True)
GLib.Error: gst_parse_error: no element "filesrc" (1)

But gst-inspect-1.0 filesrc exists and if I run the pipeline on the command
line:

gst-launch-1.0  filesrc
location="/mnt/storage/2cam/20190608_024819/capture_00000000.mkv" !
matroskademux name=demux demux.video_0 ! h264parse ! avdec_h264 !
xvimagesink

It works fine. What am I doing wrong?

I verified the string passed in is the above statement sans
'gst-launch-1.0'. And I'm importing gst with:

gi.require_version('Gst', '1.0')
from gi.respository import Gst

-aps
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