Find consecutive rows with python

I have a document with a content similar to

the line 1 is:
a-b-o 
the line 2 is:
not found
the line 3 is:
not found
the line 4 is:
a-c-k
the line 5 is:
a-d-g
a-h-o
the line 6 is:
a-g-i
the line 7 is:
not found

this. I want to use python to get successive lines of content, not the lines of not found. Taking the above as an example, the result I want to get is

the line 4 is:
a-c-k
the line 5 is:
a-d-g
a-h-o
the line 6 is:
a-g-i

Mar.15,2021

I don't know if your file is big or not. If it is not big, you can read it at once and mark it as txt , and then use "not found" to divide txt , special judgment txt [0] and txt [- 1] ; for the remaining txt [x] , if there are more than two "line" strings in the content, this means that this meets the requirements, do a processing, and then output
if the file is relatively large, you can read part of it, and then determine the location of the connection, and the rest will be handled as described above

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