def __get_keys(self, chrom, start, end=None):
keys = []<EOL>if chrom in self.whole_chrom_files:<EOL><INDENT>keys.append(self.whole_chrom_files[chrom])<EOL><DEDENT>if chrom in self.partial_trees:<EOL><INDENT>if end is not None:<EOL><INDENT>hits = self.partial_trees[chrom].intersectingInterval(start, end)<EOL><DEDENT>else:<EOL><INDENT>hits = self.partial_trees[chrom].intersectingPoint(start, end)<EOL><DEDENT>for hit in hits:<EOL><INDENT>keys.append(hit.key)<EOL><DEDENT><DEDENT>return keys<EOL>
Get the hash keys in whole/partial_chrom_files that overlap the interval.

:return: list of hash keys.