title: A problem from python crash course by google
body: <p>The group_list function accepts a group name and a list of members, and returns a string with the format: group_name: member1, member2, … For example, group_list("g", ["a","b","c"]) returns "g: a, b, c". Fill in the gaps in this function to do that.   </p>
  
  <pre><code>def group_list(group, users):
    members = ___
    return ___
  
  print(group_list("Marketing", ["Mike", "Karen", "Jake", "Tasha"])) # Should be "Marketing: Mike, Karen, Jake, Tasha"
  print(group_list("Engineering", ["Kim", "Jay", "Tom"])) # Should be "Engineering: Kim, Jay, Tom"
  print(group_list("Users", "")) # Should be "Users:"
  </code></pre>
  
  <p><strong>I have tried sth like this:</strong></p>
  
  <pre><code>members = " " 
  for i in users:
      members += ",".join(i)
  return ("{}:{}".format(group, members))
  </code></pre>
  
  <p>output comes:</p>
  
  <pre class="lang-none prettyprint-override"><code>Marketing: M,i,k,eK,a,r,e,nJ,a,k,eT,a,s,h,a
  Engineering: K,i,mJ,a,yT,o,m
  Users: 
  </code></pre>
  
  <p><strong>but it didn't give the expected answer. Can anyone solve it with filling the blanks please ?</strong></p>