code: def create(self,*fields,**kw):
          
          self.mode = mode = kw.get("mode",None)
          if os.path.exists(self.name):
              if not os.path.isfile(self.name):
                  raise IOError,"%s exists and is not a file" %self.name
              elif mode is None:
                  raise IOError,"Base %s already exists" %self.name
              elif mode == "open":
                  return self.open()
              elif mode == "override":
                  os.remove(self.name)
          self.fields = list(fields)
          self.records = {}
          self.next_id = 0
          self.indices = {}
          self.commit()
          return self
docs: Create a new base with specified field names
          A keyword argument mode can be specified ; it is used if a file
          with the base name already exists
          - if mode = 'open' : open the existing base, ignore the fields
          - if mode = 'override' : erase the existing base and create a
          new one with the specified fields