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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def bars(n=3,n_categories=3,prefix='category',columns=None,mode='abc'):
 	""" 	Returns a DataFrame with the required format for 	a bar plot 	Parameters: 		n : int 			Number of points for each trace 		n_categories : int 			Number of categories for each point 		prefix : string 			Name for each category 		columns : [str] 			List of column names 		mode : string 			Format for each item 				'abc' for alphabet columns 				'stocks' for random stock names 	"""
		
	categories=[]
	if not columns:
		columns=getName(n,mode=mode)
	for i in range(n_categories):
		categories.extend([prefix+str(i+1)])
	data=dict([(x,np.random.randint(1,100,n_categories)) for x in columns])
	return pd.DataFrame(data,index=categories)