PyFile:Nonlocal.py
  PyNonlocalStatement
    PsiElement(Py:NONLOCAL_KEYWORD)('nonlocal')
    PsiWhiteSpace(' ')
    PyTargetExpression: a
      PsiElement(Py:IDENTIFIER)('a')
    PsiElement(Py:COMMA)(',')
    PsiWhiteSpace(' ')
    PyTargetExpression: b
      PsiElement(Py:IDENTIFIER)('b')