docs: def get_signature_names(self):
          """
               Return a list of the signature file names.
          """
          signature_expr = re.compile("^(META-INF/)(.*)(\.RSA|\.EC|\.DSA)$")
          signatures = []
  
          for i in self.get_files():
              if signature_expr.search(i):
                  signatures.append(i)
  
          if len(signatures) > 0:
              return signatures
  
          return None