def infer_delimiter(filepath):
ext = os.path.splitext(filepath)[<NUM_LIT:1>][<NUM_LIT:1>:].lower()<EOL>return {"<STR_LIT>": "<STR_LIT:\t>", "<STR_LIT>": "<STR_LIT:\t>", "<STR_LIT>": "<STR_LIT:U+002C>"}.get(ext)<EOL>
From extension infer delimiter used in a separated values file.

:param str filepath: path to file about which to make inference
:return str | NoneType: extension if inference succeeded; else null