code: func (c *Call) isPreReq(other *Call) bool {
  	for _, preReq := range c.preReqs {
  		if other == preReq || preReq.isPreReq(other) {
  			return true
  		}
  	}
  	return false
  }
docs: // isPreReq returns true if other is a direct or indirect prerequisite to c.