31032021: sequence file file index check

[ami-day]

Describe the issue

• Test name: sequence file file index check
• Test Description: checks that the number of read1, read2 and index1 files are equal within a group of files with the same cell suspension id and/or process id
• Cypher query:

  <Fill in a Cypher query or suggest a human-readable test>

Acceptance criteria

• [ ] The test has been reviewed
• [ ] The test has been implemented into the graph_test_set folder

[ESapenaVentura]

This is overseeded by the resolution on ticket #11