code: def requirement_spec(package_name, *args):
      
      if not args or args == (None,):
          return package_name
      version_specs = []
      for version_spec in args:
          if isinstance(version_spec, (list, tuple)):
              operator, version = version_spec
          else:
              assert isinstance(version_spec, str)
              operator = "=="
              version = version_spec
          version_specs.append("%s%s" % (operator, version))
      return "%s%s" % (package_name, ",".join(version_specs))
docs: Identifier used when specifying a requirement to pip or setuptools.