def validate_non_negative_int_or_basestring(option, value):
    """Validates that 'value' is an integer or string.
    """
    if isinstance(value, integer_types):
        return value
    elif isinstance(value, string_type):
        try:
            val = int(value)
        except ValueError:
            return value
        return validate_non_negative_integer(option, val)
    raise TypeError("Wrong type for %s, value must be an "
                    "non negative integer or a string" % (option,))
Validates that 'value' is an integer or string.
    
stackoverflow/venv/lib/python3.6/site-packages/pymongo/common.py