<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _find_usage_api_keys(self):
 """ Find usage on API Keys. Update `self.limits`. """

        logger.debug('Finding usage for API Keys')
        key_count = 0
        paginator = self.conn.get_paginator('get_api_keys')
        for resp in paginator.paginate():
            key_count += len(resp['items'])
        self.limits['API keys per account']._add_current_usage(
            key_count, aws_type='AWS::ApiGateway::ApiKey'
        )