code: def eval(self, expression, vm='python'):
          
  
          if vm == 'numexpr':
              import numexpr as ne
              return ne.evaluate(expression, local_dict=self)
          else:
              if PY2:
                  # locals must be a mapping
                  m = {k: self[k] for k in self.dtype.names}
              else:
                  m = self
              return eval(expression, dict(), m)
docs: Evaluate an expression against the table columns.
  
          Parameters
          ----------
          expression : string
              Expression to evaluate.
          vm : {'numexpr', 'python'}
              Virtual machine to use.
  
          Returns
          -------
          result : ndarray