code: def contains(self, other):
          
          return (self.alt == other.alt and
                  self.prefix.endswith(other.prefix) and
                  self.suffix.startswith(other.suffix))
docs: Is the other VariantSequence a subsequence of this one?
  
          The two sequences must agree on the alt nucleotides, the prefix of the
          longer must contain the prefix of the shorter, and the suffix of the
          longer must contain the suffix of the shorter.