code: def to_int64(a):
      
      # build new dtype and replace i4 --> i8
      def promote_i4(typestr):
          if typestr[1:] == 'i4':
              typestr = typestr[0]+'i8'
          return typestr
  
      dtype = [(name, promote_i4(typestr)) for name,typestr in a.dtype.descr]
      return a.astype(dtype)
docs: Return view of the recarray with all int32 cast to int64.