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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 index_bowtie(self):
 """Create an index on the fasta file compatible with bowtie2."""

        # It returns exit code 1 if the fasta is empty #
        assert self
        # Call the bowtie executable #
        sh.bowtie2_build(self.path, self.path)
        return FilePath(self.path + '.1.bt2')