title: julia UndefVarError: unshift! not defined
body: <p>I use julia 1.4, and running the following code:</p>
  <pre><code>using PyCall
  using JLD
  using ArgParse
  using Pandas
  @pyimport networkx as nx
  @pyimport scipy.sparse.csgraph as csg
  @pyimport numpy as np
  
  unshift!(PyVector(pyimport(&quot;sys&quot;)[&quot;path&quot;]), &quot;&quot;)
  # unshift!(PyVector(pyimport(&quot;sys&quot;)[&quot;path&quot;]), &quot;..&quot;)
  unshift!(PyVector(pyimport(&quot;sys&quot;)[&quot;path&quot;]), &quot;combinatorial&quot;)
  @pyimport utils.load_graph as lg
  @pyimport utils.distortions as dis
  @pyimport graph_util as gu
  ....
  </code></pre>
  <p>when I run this code, I get the following error:</p>
  <pre><code> ERROR: LoadError: UndefVarError: unshift! not defined
  Stacktrace:
   [1] top-level scope at /root/hyperbolics/combinatorial/comb.jl:9
   [2] include(::Module, ::String) at ./Base.jl:377
   [3] exec_options(::Base.JLOptions) at ./client.jl:288
   [4] _start() at ./client.jl:484
  in expression starting at /root/hyperbolics/combinatorial/comb.jl:9
  </code></pre>
  <p>When I searched documents, unshift! is existing function in julia 1.4, so I don't get why this error occurs. I'm new to julia, please help.</p>