What is my mistake?
Question: This is my rexster.xml file configured as below

    
    
      <?xml version="1.0" encoding="UTF-8"?>
       <rexster>
            <http>
               <server-port>8182</server-port>
                <server-host>0.0.0.0</server-host>
                <base-uri>http://localhost</base-uri>
                <web-root>public</web-root>
                <character-set>UTF-8</character-set>
                <enable-jmx>false</enable-jmx>
                <enable-doghouse>true</enable-doghouse>
                <max-post-size>2097152</max-post-size>
                <max-header-size>8192</max-header-size>
                <upload-timeout-millis>30000</upload-timeout-millis>
                <thread-pool>
                <worker>
                    <core-size>8</core-size>
                    <max-size>8</max-size>
                </worker>
                <kernal>
                    <core-size>4</core-size>
                    <max-size>4</max-size>
                </kernal>
                </thread-pool>
                     <io-strategy>leader-follower</io-strategy>
            </http>
            <rexpro>
                <server-port>8184</server-port>
                 <server-host>0.0.0.0</server-host>
                 <session-max-idle>1790000</session-max-idle>
                 <session-check-interval>3000000</session-check-interval>
                 <connection-max-idle>180000</connection-max-idle>
                  <connection-check-interval>3000000</connection-check-interval>
                  <enable-jmx>false</enable-jmx>
                  <thread-pool>
             <worker>
                <core-size>8</core-size>
                <max-size>8</max-size>
            </worker>
            <kernal>
                <core-size>4</core-size>
                <max-size>4</max-size>
            </kernal>
             </thread-pool>
              <io-strategy>leader-follower</io-strategy>
          </rexpro>
           <shutdown-port>8183</shutdown-port>
           <shutdown-host>127.0.0.1</shutdown-host>
          <script-engine-reset-threshold>-1</script-engine-reset-threshold>
          <script-engine-init>data/init.groovy</script-engine-init>
          <script-engines>gremlin-groovy</script-engines>
          <security>
              <authentication>
                    <type>none</type>
                     <configuration>
                <users>
                    <user>
                        <username>rexster</username>
                        <password>rexster</password>
                    </user>
                </users>
            </configuration>
        </authentication>
             </security>
         <graphs>
    
           <graph>
            <graph-name>ramgraph</graph-name>
            <graph-type>tinkergraph</graph-type>
            <graph-mock-tx>false</graph-mock-tx>
        <properties>
                <storage.backend>cassandra</storage.backend>
        <storage.hostname>localhost</storage.hostname>
                <storage.buffer-size>100</storage.buffer-size>
            </properties>
            <extensions>
                <allows>
                    <allow>tp:gremlin</allow>
                </allows>
            </extensions>
        </graph>
    
    
    
        <graph>
            <graph-name>titanexample</graph-name>
                <graphtype>com.thinkaurelius.titan.tinkerpop.rexster.TitanGraphConfiguration</graph-type>
            <graph-location>/tmp/titan</graph-location>
            <graph-read-only>false</graph-read-only>
            <properties>
                <storage.backend>local</storage.backend>
                <storage.buffer-size>100</storage.buffer-size>
            </properties>
            <extensions>
            <allows>
                <allow>tp:gremlin</allow>
            </allows>
           </extensions>
       </graph>
    
    
    
    
    
          </graphs>
      </rexster>
    

and i wrote a python client with bulbs like as below

    
    
       __author__ = 'rponnapureddy'
       from bulbs.config import Config, DEBUG
       from bulbs.rexster import Graph
    
       from bulbs.rexster import Graph
    
       # config = Config('http://localhost:8182/graphs/empgraph')
       config = Config('http://localhost:8182/graphs/ramgraph')
    
       g = Graph(config)
    
       class inser_class():
           ponnapu = g.vertices.create(name="ramnath")
           pr = g.vertices.create(name="reddy")
           tanu = g.vertices.create(name="brothers")
           g.edges.create(pr, "knows", tanu)
           # z=g.get_graphml()
           #print z
           #g.clear()
           # print z
    

I got below error . To correct answer what i have do ?

'usr/bin/python2.7 "/home/rpo/Desktop/ramnathreddy/addverices to
rexsterdefault graph.py" Traceback (most recent call last): File
"/home/rpo/Desktop/ramnath/addverices to rexsterdefault graph.py", line 10, in
g = Graph(config) File "/usr/local/lib/python2.7/dist-
packages/bulbs/rexster/graph.py", line 56, in **init** super(Graph,
self).**init**(config) File "/usr/local/lib/python2.7/dist-
packages/bulbs/base/graph.py", line 58, in **init** self.vertices =
self.build_proxy(Vertex) File "/usr/local/lib/python2.7/dist-
packages/bulbs/base/graph.py", line 124, in build_proxy return
self.factory.build_element_proxy(element_class, index_class) File
"/usr/local/lib/python2.7/dist-packages/bulbs/factory.py", line 19, in
build_element_proxy primary_index =
self.get_index(element_class,index_class,index_name) File
"/usr/local/lib/python2.7/dist-packages/bulbs/factory.py", line 27, in
get_index index = index_proxy.get_or_create(index_name) File
"/usr/local/lib/python2.7/dist-packages/bulbs/rexster/index.py", line 80, in
get_or_create resp = self.client.get_or_create_vertex_index(index_name,
index_params) File "/usr/local/lib/python2.7/dist-
packages/bulbs/rexster/client.py", line 668, in get_or_create_vertex_index
resp = self.gremlin(script, params) File "/usr/local/lib/python2.7/dist-
packages/bulbs/rexster/client.py", line 356, in gremlin return
self.request.post(gremlin_path, params) File "/usr/local/lib/python2.7/dist-
packages/bulbs/rest.py", line 131, in post return self.request(POST, path,
params) File "/usr/local/lib/python2.7/dist-packages/bulbs/rest.py", line 186,
in request return self.response_class(http_resp, self.config) File
"/usr/local/lib/python2.7/dist- packages/bulbs/rexster/client.py", line 198,
in **init** self.handle_response(response) File
"/usr/local/lib/python2.7/dist-packages/bulbs/rexster/client.py", line 222, in
handle_response response_handler(http_resp) File
"/usr/local/lib/python2.7/dist-packages/bulbs/rest.py", line 50, in
server_error raise SystemError(http_resp) SystemError: ({'status': '500',
'transfer-encoding': 'chunked', 'server': 'grizzly/2.2.16', 'connection':
'close', 'date': 'Mon, 16 Mar 2015 11:32:19 GMT', 'access-control-allow-
origin': '*', 'content-type': 'application/json'},
'{"message":"","error":"javax.script.ScriptException:
groovy.lang.MissingMethodException: No signature of method:
groovy.lang.MissingMethodException.rollback() is applicable for argument
types: () values: []\nPossible solutions: collect(),
collect(groovy.lang.Closure), collect(java.util.Collection,
groovy.lang.Closure)","api":{"description":"evaluate an ad-hoc Gremlin script
for a graph.","parameters":{"rexster.returnKeys":"an array of element property
keys to return (default is to return all element
properties)","rexster.showTypes":"displays the properties of the elements with
their native data type (default is false)","load":"a list of \'stored
procedures\' to execute prior to the \'script\' (if \'script\' is not
specified then the last script in this argument will return the
values","rexster.offset.end":"end index for a paged set of data to be
returned","rexster.offset.start":"start index for a paged set of data to be
returned","params":"a map of parameters to bind to the script
engine","language":"the gremlin language flavor to use (default to
groovy)","script":"the Gremlin script to be evaluated"}},"success":false}')

    
    
    Process finished with exit code 1'
    


Answer: 
    from bulbs.config import Config, DEBUG
    from bulbs.rexster import Graph
    from bulbs.titan import Graph
    
    config = Config('http://localhost:8182/graphs/ramgraph')
    g = Graph(config)
    
    
    class inser_class():
        ponnapu = g.vertices.create(name="reddy", age="26", state="TELNGANA", mobn="111111111")
        pr = g.vertices.create(name="ramnath" ,age="25" , state="TELNGANA", mobn="1111111")
        tanu = g.vertices.create (name="ponnapu",age="27",state="AP",mobn="11111111111111")
        g.edges.create(pr, "knows", tanu)
        g.edges.create(pr, "friends", ponnapu)
        g.edges.create(ponnapu, "dontknow",tanu)
    

