code: def deps(spec):
      """Get PEP 440 dependency requirements for a craft spec.
  
      Parameters
      ----------
      spec : str, sktime/skbase compatible object specification
          i.e., a string that executes to construct an object if all imports were present
          imports inferred are of any classes in the scope of ``all_estimators``
          option 1: a string that evaluates to an estimator
          option 2: a sequence of assignments in valid python code,
              with the object to be defined preceded by a "return"
              assignments can use names of classes as if all imports were present
  
      Returns
      -------
      reqs : list of str
          each str is PEP 440 compatible requirement string for craft(spec)
          if spec has no requirements, return is [], the length 0 list
      """
      register = dict(all_estimators())
  
      dep_strs = []
  
      for x in _extract_class_names(spec):
          if x not in register.keys():
              raise RuntimeError(
                  f"class {x} is required to build spec, but was not found "
                  "in all_estimators scope"
              )
          cls = register[x]
  
          new_deps = cls.get_class_tag("python_dependencies")
  
          if isinstance(new_deps, list):
              dep_strs += new_deps
          elif isinstance(new_deps, str) and len(new_deps) > 0:
              dep_strs += [new_deps]
  
          reqs = list(set(dep_strs))
  
      return reqs
  
imports: import re
  from sktime.registry._lookup import all_estimators
label_desc: Use image node_id 3 for calling a global function with example usage: deps(spec) and returns: reqs