def _make_row(row, conversions):
  """Builds a python native row from proto3 row.

  Args:
    row: proto3 row
    conversions: conversion function array

  Returns:
    an array of converted rows.
  """
  converted_row = []
  offset = 0
  for i, l in enumerate(row.lengths):
    if l == -1:
      converted_row.append(None)
    elif conversions[i]:
      converted_row.append(conversions[i](row.values[offset:offset+l]))
      offset += l
    else:
      converted_row.append(row.values[offset:offset+l])
      offset += l
  return converted_row