code: def make_name_ac_map(assy_name, primary_only=False):
      
      return {
          s['name']: s['refseq_ac']
          for s in get_assembly(assy_name)['sequences']
          if (not primary_only or _is_primary(s))
      }
docs: make map from sequence name to accession for given assembly name
  
      >>> grch38p5_name_ac_map = make_name_ac_map('GRCh38.p5')
      >>> grch38p5_name_ac_map['1']
      'NC_000001.11'