code: def change_lines_in_svg(self,filename, string1,string2):
  		
  		for i,line in enumerate(fileinput.input(filename, inplace=1)):
  			sys.stdout.write(line.replace(str(string1),str(string2)))
docs: Used to change lines in an SVG file. String1 is input - what is already present
  		in the file, while string2 is output - the desired line. The input has to be searchable
  		since .replace function is used.
  		Takes:
  			* filename * - name of the SVG file to change
  			* string1 * - input string
  			* string2 * - output string