@property<EOL><INDENT>def ncbi_geneid(self):<DEDENT>
values = self.get_attribute('<STR_LIT>', as_list=True)<EOL>if values is None:<EOL><INDENT>return None<EOL><DEDENT>for value in values:<EOL><INDENT>if value.startswith('<STR_LIT>'):<EOL><INDENT>key, geneid = value.split('<STR_LIT::>')<EOL>return geneid<EOL><DEDENT><DEDENT>return None<EOL>
Retrieve this feature's NCBI GeneID if it's present.

NCBI GFF3 files contain gene IDs encoded in **Dbxref** attributes
(example: `Dbxref=GeneID:103504972`). This function locates and returns
the GeneID if present, or returns `None` otherwise.