FormalML: A Benchmark for Evaluating Formal Subgoal Completion in Machine Learning Theory - Yang, Xiao-Wen; Zhang, Zihao; Cao, Jianuo; Zhou, Zhi; Li, Zenan; Guo, Lan-Zhe; Yao, Yuan; Chen, Taolue; Li, Yu-Feng; Ma, Xiaoxing (International Conference on Learning Representations, 2026)