docs: def filter(self, filters):
          '''
          Apply filters to the pileup elements, and return a new Pileup with the
          filtered elements removed.
  
          Parameters
          ----------
          filters : list of PileupElement -> bool callables
              A PileupUp element is retained if all filters return True when
              called on it.
          '''
          new_elements = [
              e for e in self.elements
              if all(function(e) for function in filters)]
          return Pileup(self.locus, new_elements)