AWS lambda give permission to assume role

I want to use role assume in a AWS lambda function.

I have the follow template.yml

AWSTemplateFormatVersion: '2010-09-09'Transform: AWS::Serverless-2016-10-31Parameters:  Role1:    Type: StringResources:  Function1:    Type: 'AWS::Serverless::Function'    Properties:      Handler: core.lambda_function.lambda_handler      Policies:        - Statement:            - Sid: AssumeRol              Effect: Allow              Action:                - sts:AssumeRole              Resource: '*'      Environment:        Variables:          ROLE: !Ref Role1

And in lambda python the follow code:

role_arn = get_role_arn_from_env_parameter()assumed_role_object = sts_client.assume_role(                    RoleArn=role_arn,                    RoleSessionName="AssumeRoleSession")

But I get the follow error when functions is executed:

ClientError: An error occurred (AccessDenied) when calling the AssumeRole operation:User: "..." is not authorized to perform: sts:AssumeRole on resource: "..."

It seems Policy Statement AssumeRol does not work or maybe should be put in other place ?

EDIT:trusted role policy:

{"Version": "2012-10-17","Statement": [        {"Sid": "Statement1","Effect": "Allow","Principal": {"Service": "lambda.amazonaws.com"            },"Action": "sts:AssumeRole"        }    ]}