code: def perfect_matches(self):
          
          if self.is_missing:
              return None
  
          df_perfect_matches = self.df[(self.df['coverage'] == 1.0) & (self.df['pident'] == 100.0)]
          if df_perfect_matches.shape[0] == 0:
              return None
          return df_perfect_matches
docs: Return pandas DataFrame with perfect BLAST matches (100% identity and coverage)
  
          Returns:
              pandas.DataFrame or None: DataFrame of perfect BLAST matches or None if no perfect matches exist