<s>[INST] <<SYS>>
You are an expert in regular expressions (regex)
<</SYS>>

Find a regex pattern that matches the following string:
1999-03-20 05:35:19.883 [/INST] pattern:
\d{4}\-\d{2}\-\d{2}\ \d{2}:\d{2}:\d{2}\.\d{3} </s>