runtime error

Exit code: 1. Reason: Traceback (most recent call last): File "/home/user/app/app.py", line 15, in <module> from agents import news_researcher, news_writer File "/home/user/app/agents.py", line 2, in <module> from tools import tool File "/home/user/app/tools.py", line 7, in <module> os.environ['SERPER_API_KEY'] = os.getenv('SERPER_API_KEY') File "/usr/local/lib/python3.10/os.py", line 685, in __setitem__ value = self.encodevalue(value) File "/usr/local/lib/python3.10/os.py", line 757, in encode raise TypeError("str expected, not %s" % type(value).__name__) TypeError: str expected, not NoneType

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