Hello: 
    As a first step to my question, let  G be  a graph and  I'd like to know  whether it contains a C₄ (cycle of 4) as its subgraph.
     For example: .   It contains C₄. So  program may be return true.  
    I'm most concerned about the following thing ( it is important problem for me, since in graph theory, we usually consider some class graphs contain no sepecific graph ) :
   1 Further , I want to  get all connected graphs of order less than 6  which  contains no C₄ .
   2 More generally, I want  to konw  a graph  whether contains some graph as its subgraph.For example : does it contain K4CompleteGraph(4) ，K32  CompleteGraph(3, 2)  and so on ?
    I read the  function subgaph.  But  It didn't solve my problem. Many thanks for your help or advise.
   # I  just know there is a function  IsTriangleFree which test if graph is triangle-free ( graph comtains no C₃)  in Maple 2019. I think my question and how to program may be  meaningful.

 Hello!
  As we  known, in Graphtheory , a loop is an edge that joins a vertex to itself (for example  fig1 vertex1) and multiple edges (for example Fig2）are two or more edges that join the same two vertices.  But in Maple,  G := Graph({{a, b}, {a, c}, {b, c}}). The Edges(G) function returns a set  (not list )of the edges of G.  So, for example I can't create loop{1,1} by G:=Graph({{1,1},{1,2},{1,5},{2,5},{2,3},{5,4},{3,4},{4,6}})   . But in my research, I consider a graph which exist loops or multiple edges. I want to create  it  .How should I do?  Thanks in advance.

my code like this

with(GraphTheory):
G:=Graph({{1,2},{1,5},{2,5},{2,3},{5,4},{3,4},{4,6}}):
G:=Graph({{1,1},{1,2},{1,5},{2,5},{2,3},{5,4},{3,4},{4,6}}):DrawGraph(G,style=spring);
G2:=Graph({{1,2}}):
DrawGraph(G2);
G3:=Graph({{1,2},{1,2}}):
DrawGraph(G3);

Hello, everyone: I have a question of drawing graph。
restart:
with(GraphTheory):
with(SpecialGraphs):
H := HypercubeGraph(3):
DrawGraph(H,style = spring);

How  do I change  the vertex style   to polygon without line.
the aim graph  like figure below:

Thank you very much!

 Given  any graph , I want to  determine the number of cycles of the graph .  What should I do?