remove pagebreak after part

I am use the book documentclass with various parts. For a part, I’d like the Part number and title followed by a paragraph on the same page. Currently, I’m getting the Part number and title on a page, with the rest of the page blank, the following page blank and then a page with the paragraph.

Also, I’m using the titlesec package to reformat them and realize there is spacing in the titleformat command, but it appears that no control over the spacing will remove the page break.

I also tried refining @endpart, however that didn’t work. I wonder if this conflicts with the titlesec package.

Edited Below

With the answer below, here’s a twist on the code with titleformat defined which shows that redefining @endpart doesn’t seem to work:

documentclass{book}
usepackage{titlesec}
usepackage{lipsum}

titleformat{part}
  {hugesffamilyslshape}
  {Part~thepart:}{1em}{}

begin{document}

makeatletter
renewcommand{@endpart}{}
makeatother

part{A part}
vspace{2baselineskip}
lipsum[1]

cleardoublepage
lipsum[2]

end{document}

documentclass{book}
usepackage{titlesec}
usepackage{etoolbox}
usepackage{lipsum}

makeatletter
patchcmd{ttl@page@ii}{newpageif@twoside}{iffalse}{}{}
makeatother

titleformat{part}
  {hugesffamilyslshape}
  {Part~thepart:}{1em}{}

begin{document}

part{A part}
vspace{2baselineskip}
lipsum[1]

cleardoublepage
lipsum[2]

end{document}

% partpageprob.tex  SE 553544
documentclass{book}
usepackage{titlesec}
usepackage{lipsum}

begin{document}

makeatletter
renewcommand{@endpart}{}
makeatother

part{A part}
vspace{2baselineskip}
lipsum[1]

cleardoublepage
lipsum[2]

end{document}