code: def missing(self, field, last=True):
          '''
          Numeric fields support specific handling for missing fields in a doc.
          The missing value can be _last, _first, or a custom value
          (that will be used for missing docs as the sort value).
  
          missing('price')
          > {"price" : {"missing": "_last" } }
          missing('price',False)
          > {"price" : {"missing": "_first"} }
          '''
          if last:
              self.append({field: {'missing': '_last'}})
          else:
              self.append({field: {'missing': '_first'}})
  
          return self missing(self, field, last=True):
          '''
          Numeric fields support specific handling for missing fields in a doc.
          The missing value can be _last, _first, or a custom value
          (that will be used for missing docs as the sort value).
  
          missing('price')
          > {"price" : {"missing": "_last" } }
          missing('price',False)
          > {"price" : {"missing": "_first"} }
          '''
          if last:
              self.append({field: {'missing': '_last'}})
          else:
              self.append({field: {'missing': '_first'}})
  
          return self
docs: Numeric fields support specific handling for missing fields in a doc.
          The missing value can be _last, _first, or a custom value
          (that will be used for missing docs as the sort value).
  
          missing('price')
          > {"price" : {"missing": "_last" } }
          missing('price',False)
          > {"price" : {"missing": "_first"} }