has<T> method
check if one dependency is available to call to the find method
Implementation
bool has<T>({String? tag}) {
final key = _getKey(T, tag);
final inVars = _vars.containsKey(key);
if (inVars) return true;
final inFactoryVars = _factoryVars.containsKey(key);
if (inFactoryVars) return true;
final inLazyVars = _lazyVars.containsKey(key);
return inLazyVars;
}