BibtexParser.check_string

You're seeing just the function check_string, go back to BibtexParser module for more information.
Link to this function

check_string(str)

Given a string containing bibtex content, parses the string and then runs checks on it to verify if the content is proper bibtex. These checks can be both structural (e.g., empty fields) and semantic (e.g. required fields).

Each error returned from the function is in the form of {<label>, [<error>: message]}.

Examples

iex(4)> BibtexParser.check_string("@incollection{foo, title={Bar}")
[{"foo", [missing_tags: ["author", "booktitle", "pages", "publisher", "year"]]}]