Font family name for Josefin Sans

What is the font family name for Josefin sans? I know that the font can be set by adding

usepackage{josefin}

in the preamble. However, I am trying to change the chapter heading style using the package secsty,

usepackage{sectsty}

And there I need to provide the font family name

chapterfont{fontfamily{Font Family Name Goes Here}selectfont}

Therefore, I need to know the font family name for the josefin font. What is the font family name for the josefin font? Moreover, how to know the font family names for different fonts in general, as in is there a list of some kind?

If there is any alternative method to change the fonts for chapter headings without using the font family name but using the package name directly, please suggest so. (Note that I intend to use different fonts for the chapter/section headings and the text in the body)

documentclass{article}
usepackage{josefin}

begin{document}
makeatletter
sffamily the family name is f@family 
makeatother
end{document}

documentclass{book}
usepackage{cmbright}
edeffamilydefault{familydefault}
usepackage{josefin}
usepackage{sectsty}

chapterfont{sffamily}

begin{document}

chapter{Title}

Some text in CM Bright. Also math $a+b=sum_{i=1}^n x_i$.

end{document}