docs: def from_file(filename):
          """Read in filename and creates a trace object.
  
          :param filename: path to nu(x|s)mv output file
          :type filename: str
          :return:
          """
          trace = Trace()
          reached = False
          with open(filename) as fp:
              for line in fp.readlines():
                  if not reached and line.strip() == "Trace Type: Counterexample":
                      reached = True
                      continue
                  elif reached:
                      trace.parse_line(line)
              return trace