code: def exists_uda(self, name, database=None):
          
          return len(self.list_udas(database=database, like=name)) > 0
docs: Checks if a given UDAF exists within a specified database
  
          Parameters
          ----------
          name : string, UDAF name
          database : string, database name
  
          Returns
          -------
          if_exists : boolean