docs: def parse_yaml(self, y):
          '''Parse a YAML spefication of an execution context into this
          object.
  
          '''
          self.id = y['id']
          self.kind = y['kind']
          if 'rate' in y:
              self.rate = float(y['rate'])
          else:
              self.rate = 0.0
          self._participants = []
          if 'participants' in y:
              for p in y.get('participants'):
                  self._participants.append(TargetComponent().parse_yaml(p))
          if RTS_EXT_NS_YAML + 'properties' in y:
              for p in y.get(RTS_EXT_NS_YAML + 'properties'):
                  if 'value' in p:
                      value = p['value']
                  else:
                      value = None
                  self._properties[p['name']] = value
          return self