In TeXForm#
TeXForm parses this entry as a character leaf mapped to U+219E (LEFTWARDS TWO HEADED ARROW).
\to\rightarrow\longrightarrow\mapsto\xrightarrow\Rightarrow\Leftrightarrow\leftarrow\longmapsto\hookrightarrow\Longrightarrow\twoheadleftarrow