code: def percent_covered(self, src_path):
          
          diff_violations = self._diff_violations().get(src_path)
  
          if diff_violations is None:
              return None
  
          # Protect against a divide by zero
          num_measured = len(diff_violations.measured_lines)
          if num_measured > 0:
              num_uncovered = len(diff_violations.lines)
              return 100 - float(num_uncovered) / num_measured * 100
  
          else:
              return None
docs: Return a float percent of lines covered for the source
          in `src_path`.
  
          If we have no coverage information for `src_path`, returns None