You really don't need any packages for this
\documentclass{article}
\begin{document}
\begin{picture}(100,100)
\put(43,56){\circle{6}}
\put(43,56){\circle*{1}}
\put(57,56){\circle{6}}
\put(57,56){\circle*{1}}
\put(50,45){\circle{12}}
\put(48,45){\oval(3,5)}
\put(52,45){\oval(3,5)}
\put(50,50...
The full message is
! LaTeX Error: Missing \begin{document}.
See the LaTeX manual or LaTeX Companion for explanation.
Type H <return> for immediate help.
...
l.7364 \RHUBARB
% %...
@DavidCarlisle but it starts to error in texlive 2018. Why didn't they repair it in the last three years? Or did they and this is an outdated version of the class?
@UlrikeFischer a lot of IEEE journals provide a class called IEEEtrans.cls with a \ProvideClass{ieeecolor} in the first line since... since... boh, forever. Nobody corrects it (not citing that they have a bug in the color stack too).
@DavidCarlisle -- That's the ultimate cause of the problem, but the way the intended "correction" to the document class was the cause of the particular error message, and you didn't mention that, which would have been instructive for the OP. I left )probably impertinent) comments.
@barbarabeeton I'm not sure it's instructive to use AtBeginDocument, which also shouldn't be used for typesetting and as I commented under egreg's answer the actual definition with a smashed \_ seems to be nonsense, they want an empty hbox (which they shouldn't want either) but it's a journal class the end user doesn't need to fix it the journal will do whatever it needs to do, so just making the error go so the document can be processed seems to be enough
@DavidCarlisle -- I think it's helpful to say why a particular error is reported -- it's instructive to a newbie to learn that the error Missing \begin{document} has to be something that happened in the preamble or document class, so it cuts down the list of things that need to be looked at. Granted the OP didn't provide the full error message, so you had to find it yourself. And I agree that \AtBeginDocument isn't the right thing to do here. As I said, "impertinent".
@barbarabeeton well it is reported because we changed latex, and some nonsensical command that previously silently did something nonsensical generates an error. But I'm not sure that's useful information to a beginner.
@DavidCarlisle -- You'll not change my belief that the more a (La)TeX user knows about debugging, the better off they are in coping with the inevitable.
@barbarabeeton in a normal case I'd have gone on to say what the error meant and how to fix the input but here the input was nonsensical and the error message essentially arbitrary and it's a document class supported by a commercial publisher, so I bailed out.
@DavidCarlisle -- Fair enough. But it still seems to me that in that case, knowing that the error wasn't in his part would be an indication to the OP that the supplier had caused the problem. (Too many "that"s, but I'm sure you can figure out what I'm trying to say.)
@CarLaTeX What a heartwarming story! That it so touching!
I'm very partial to opossums and platypuses and wonder if that would be accepted here.
Yesterday I discovered that an iOS app called a-shell contains the TeX engine from TeX Live 2019. I don't think LaTeX is included (but I may be wrong since I only spent about five minutes experimenting). I wasn't able to do anything useful. I think it only works with plain TeX, which I've never used. Anyway, I wasn't aware that a-shell included TeX.
You really don't need any packages for this
\documentclass{article}
\begin{document}
\begin{picture}(100,100)
\put(43,56){\circle{6}}
\put(43,56){\circle*{1}}
\put(57,56){\circle{6}}
\put(57,56){\circle*{1}}
\put(50,45){\circle{12}}
\put(48,45){\oval(3,5)}
\put(52,45){\oval(3,5)}
\put(50,50...
