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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def read_tsv(cls, file_or_buffer: str):
 """Read genes from tab-delimited text file."""

        df = pd.read_csv(file_or_buffer, sep='\t', index_col=0)
        df = df.where(pd.notnull(df), None)
        # Note: df.where(..., None) changes all column types to `object`.
        return cls(df)