    def visit_Call(self, node):
        """ A couple function calls are supported: bson's ObjectId() and
        datetime().
        """
        if isinstance(node.func, ast.Name):
            expr = None
            if node.func.id == 'ObjectId':
                expr = "('" + node.args[0].s + "')"
            elif node.func.id == 'datetime':
                values = []
                for arg in node.args:
                    values.append(str(arg.n))
                expr = "(" + ", ".join(values) + ")"
            if expr:
                self.current_value = eval(node.func.id + expr)
The software constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.