src/StateWithParams.js
function isIn(fullStateName) {
    let current = state
    while (current) {
      if (current.fullName == fullStateName) return true
      current = current.parent
    }
    return false
  }
function isIn(fullStateName) {
    let current = state
    while (current) {
      if (current.fullName == fullStateName) return true
      current = current.parent
    }
    return false
  }
/*
Returns whether this state or any of its parents has the given fullName.