Function try_parse_double_backslash_display_math 

pub fn try_parse_double_backslash_display_math(
    text: &str,
) -> Option<(usize, &str)>

Try to parse double backslash display math: \[…\] Extension: tex_math_double_backslash

Per Pandoc spec:

• Content can span multiple lines
• Double backslash is the delimiter