is_snake_case_file_name_with_extension

stringtools.is_snake_case_file_name_with_extension(expr)

Is true when expr is a string and is underscore-delimited lowercase file name with extension.

>>> stringtools.is_snake_case_file_name_with_extension('foo_bar.blah')
True

Otherwise false:

>>> stringtools.is_snake_case_file_name_with_extension('foo.bar.blah')
False

Returns true or false.