<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def annotatedcore(self):
 """ Calculates the core genome of organisms using custom databases """

        logging.info('Calculating annotated core')
        # Determine the total number of core genes
        self.total_core()
        # Iterate through all the samples, and process all Escherichia
        for sample in self.metadata:
            if sample.general.bestassemblyfile != 'NA':
                # Create a set to store the names of all the core genes in this strain
                sample[self.analysistype].coreset = set()
                if sample.general.referencegenus == 'Escherichia':
                    # Add the Escherichia sample to the runmetadata
                    self.runmetadata.samples.append(sample)
                    # Parse the BLAST report
                    try:
                        report = sample[self.analysistype].report
                        self.blastparser(report=report,
                                         sample=sample,
                                         fieldnames=self.fieldnames)
                    except KeyError:
                        sample[self.analysistype].coreset = list()
        # Create the report
        self.reporter()