ed.
- Each test vector is a sequence of 1 or more adjacent lines, where
  each lines is an assignement.
- Test vectors are separated by an empty line, a comment, or
  a line starting with "[".

A test vector object has the following attributes:

- desc (string): description
- counter (int): the order of the test vector in the file (from 1)
- others (list): zero or more lines of the test vector that were not assignments
- left-hand side of each assignment (lowercase): the value of the
  assignement, either converted or bytes.
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