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[boring_accountant]

It would be helpful to see a bit more of your code, especially how you define df_filtered. From the error message you posted it looks quite simply like you didn't define df_filtered. Some possible causes:

• variable definition comes after the first time the variable is actually used
  
• variable definition uses a slightly different name
  
• variable definition is in another scope (e.g. variable defined in a function scope and used in the global scope