title: I try using SymPy in Julia 1.7.1 and get "coeffs not found" error
body: <p>I am trying to use coeffs function in Julia 1.7.1 but getting the error below:</p>
  <p><a href="https://i.stack.imgur.com/2XB4x.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/2XB4x.png" alt="i get error while using [p0].coeffs().keys()" /></a></p>
  <p>the error occurs in the below code in the last line where i have  <code>S = [p0].coeffs().keys()</code> see the code below:</p>
  <pre><code>p0 = sympify(dense_interpolation([a[1]] .+ r, [p0] .+ P).subs(Symbol('x'), x_var[1]))
  print(&quot;[p0] = &quot;)
  println([p0])
  print(&quot;p0 = &quot;)
  println(p0)
  S = [p0].coeffs().keys()
  </code></pre>
  <p>the type of the <code>p0</code> is <code>Sym</code> and the value inside it is <code>1</code> as you can see on the first picture.
  can anyone help me out on this.</p>