docs: def decrypt_file(self, filename):
          '''
          Decrypt File
          Args:
              filename: Pass the filename to encrypt.
          Returns:
              No return.
          '''
          if not os.path.exists(filename):
              print "Invalid filename %s. Does not exist" % filename
              return
  
          if self.vault_password is None:
              print "ENV Variable PYANSI_VAULT_PASSWORD not set"
              return
  
          if not self.is_file_encrypted(filename):
              # No need to do anything.
              return
  
          cipher = 'AES256'
          vaulteditor = VaultEditor(cipher, self.vault_password, filename)
          vaulteditor.decrypt_file()