message: Added function to check trace existence
  Added function to check if a trace exists in the map.
diff: @@ -84,6 +84,13 @@ impl<'a> TraceMap<'a> {
  None
  }
  + pub fn contains_trace(&self, file: &Path, line: u64) -> bool {
  + match self.traces.get(file) {
  + Some(traces) => traces.iter().any(|x| x.line == line),
  + None => false,
  + }
  + }
  +
  /// Gets all traces below a certain path
  pub fn get_child_traces(&self, root: &Path) -> Vec<&Trace> {
  self.traces.iter()
  @@ -97,6 +104,7 @@ impl<'a> TraceMap<'a> {
  self.traces.values().flat_map(|ref x| x.iter()).collect()
  }
  + /// Gets a vector of all the traces to mutate
  fn all_traces_mut(&mut self) -> Vec<&mut Trace> {
  self.traces.values_mut().flat_map(|x| x.iter_mut()).collect()
  }
  