SHELL_SCRIPT
  COMMANDS_LIST
    GENERIC_COMMAND_DIRECTIVE
      LITERAL
        PsiElement(word)('echo')
  PsiElement(\n)('\n')
  PsiWhiteSpace(' ')
  COMMANDS_LIST
    SHELL_COMMAND
      ARITHMETIC_EXPANSION
        PsiElement(()('(')
        PsiElement(()('(')
        ASSIGNMENT_EXPRESSION
          LITERAL_EXPRESSION
            PsiElement(word)('a')
          PsiElement(=)('=')
          LITERAL_EXPRESSION
            NUMBER
              PsiElement(int)('1')
        PsiElement())(')')
        PsiElement())(')')