Almotriptan Dimer Impurity; 3-[2-(Dimethylamino)ethyl]-2-[[3-[2-(dimethylamino)ethyl]-1H-indol-5-yl]methyl]-1H-indole-5-methylsulfonylpyrrolidine;2-[[3-[2-(Dimethylamino)ethyl]-1H-indol-5-yl]methyl]-N,N-dimethyl-5-[(1-pyrrolidinylsulfonyl)methyl]-1H-indole-3-ethanamine; 2-(2-((3-(2-(Dimethylamino)ethyl)-1H-indol-5-yl)methyl)-5-((pyrrolidin-1-ylsulfonyl)methyl)-1H-indol-3-yl)-N,N-dimethylethan-1-amine;