当我缩放以下代码时
\documentclass{article}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}[scale=0.6]
[bend angle =60,inner sep=0pt, minimum size =10mm,very thick,
from/.style={<-},
towards/.style={->},
protein/.style={circle,draw=black,very thick},
reaction/.style={}]
\node[protein] (p) at (-2,0) {$\mathcal{A}$};
\node[protein] (ps) at (2,0) {$f(\mathcal{A})$}
edge [towards, bend left] node [pos=0.5, below] {$f^{-1}$} (p)
edge [from, bend right] node [pos=0.5, above] {$f$} (p) ;
\end{tikzpicture}
\end{document}
我收到以下错误
Package pgfkeys Error: I do not know the key '/tikz/towards' and I am going to ignore it. Perhaps you misspelled it. ...ft] node [pos=0.5, below] {$f^{-1}$} (p)
如果我删除了，[scale=0.6]一切都会正常，编译也会正常。发生了什么事？我该如何缩放图形？