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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 hdr_xform(self, hdrs):
 """Transform NCBI Gene header fields into valid namedtuple fields."""

        xform = []
        hdrs = self.replace_nulls(hdrs)
        for hdr in hdrs:
            hdr = hdr.replace('.', '_')
            hdr = hdr.replace(' ', '_')
            hdr = hdr.replace('#', 'N')
            hdr = hdr.replace('-', '_')
            hdr = hdr.replace('"', '')
            xform.append(hdr)
        return xform