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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 children_bp(self, feature, child_featuretype='exon', merge=False, ignore_strand=False):
 """ Total bp of all children of a featuretype. Useful for getting the exonic bp of an mRNA. Parameters feature : str or Feature instance child_featuretype : str Which featuretype to consider. For example, to get exonic bp of an mRNA, use `child_featuretype='exon'`. merge : bool Whether or not to merge child features together before summing them. ignore_strand : bool If True, then overlapping features on different strands will be merged together; otherwise, merging features with different strands will result in a ValueError. Returns ------- Integer representing the total number of bp. """


        children = self.children(feature, featuretype=child_featuretype,
                                 order_by='start')
        if merge:
            children = self.merge(children, ignore_strand=ignore_strand)

        total = 0
        for child in children:
            total += len(child)
        return total