code: def parse_names(cls, expression):
          
          names = set()
          try:
              ast_node = ast.parse(expression, "ast")
  
              class Visitor(ast.NodeVisitor):
                  def visit_Name(self, node):
                      names.add(node.id)
  
              Visitor().visit(ast_node)
          except Exception:
              pass
          return names
docs: Return the list of identifiers used in the expression.