It doesn't work my tikzcd code in beamer

Question

this code works in a normal latex document but not in beamer. Why?

\section{Project}

\subsection{General scheme}
\begin{frame}
\frametitle{General scheme}
\[
\begin{tikzcd}
A \arrow{r}{a} \arrow[bend right]{r} 
& B \arrow{r}{b} & C \arrow{r}{c}
\arrow{rd}{e} & D \arrow[bend right]{d}\\
& F \arrow{u} \arrow{rr}{f} && E
\end{tikzcd}
\]
\end{frame}

Answer 1

The problem is solved if I add \begin{frame}[fragile]