how to convert R code to rpy2?

how to convert R code to rpy2?

I have a R code sample .I want to convert to rpy2 python.I read documents
of rpy2 but not solved my problem.
R code :(2.15)
library(wordcloud)
library(tm)
a <- Corpus (DirSource("D:/Arshad/Thiese/Network
Visiualization/R-D3-SNA/text"))
inspect(a)
a <- tm_map(a, stripWhitespace)
a <- tm_map(a, tolower)
a <- tm_map(a, removeWords, stopwords("english"))
a <- tm_map(a, stemDocument)
wordcloud(a, scale=c(5,0.5), max.words=100, random.order=FALSE, rot.per=0.35,
use.r.layout=FALSE, colors=brewer.pal(8, "Dark2"))



in rpy2 i converted some lines but get errors please help me:
from rpy2.robjects.packages import importr
import rpy2.robjects as robjects
tm = importr('tm')
wordcloud=importr('wordcloud')
DirSource=tm.DirSource("D:/Arshad/Thiese/Network
Visiualization/R-D3-SNA/text" ,encoding = "UTF-8",)
a=tm.Corpus(DirSource)
a=tm.inspect(a)
a=tm.tm_map(a,tm.stripWhitespace)
error:
RRuntimeError
Traceback (most recent call last)
<ipython-input-52-40d1b0549fd2> in <module>()
7 a=tm.Corpus(DirSource)
8 a=tm.inspect(a)
----> 9 a=tm.tm_map(a,tm.stripWhitespace)
F:\Anaconda\lib\site-packages\rpy2\robjects\functions.pyc in
__call__(self, *args, **kwargs)
84 v = kwargs.pop(k)
85 kwargs[r_k] = v
---> 86 return super(SignatureTranslatedFunction,
self).__call__(*args, **kwargs)
F:\Anaconda\lib\site-packages\rpy2\robjects\functions.pyc in
__call__(self, *args, **kwargs)
33 for k, v in kwargs.iteritems():
34 new_kwargs[k] = conversion.py2ri(v)
---> 35 res = super(Function, self).__call__(*new_args, **new_kwargs)
36 res = conversion.ri2py(res)
37 return res
RRuntimeError: Error in UseMethod("tm_map", x) :
no applicable method for 'tm_map' applied to an object of class "list"