Check to see if the given modelName exists in the given restApiId

    CLI Example:

    .. code-block:: bash

        salt myminion boto_apigateway.api_model_exists restApiId modelName

def api_model_exists(restApiId, modelName, region=None, key=None, keyid=None, profile=None):
    '''
    Check to see if the given modelName exists in the given restApiId

    CLI Example:

    .. code-block:: bash

        salt myminion boto_apigateway.api_model_exists restApiId modelName
    '''
    r = describe_api_model(restApiId, modelName, region=region, key=key, keyid=keyid, profile=profile)

    return {'exists': bool(r.get('model'))}