parseObjectData(meta, data, start, count) {
    const {xScale, yScale} = meta;
    const {xAxisKey = 'x', yAxisKey = 'y'} = this._parsing;
    const parsed = new Array(count);
    let i, ilen, index, item;

    for (i = 0, ilen = count; i < ilen; ++i) {
      index = i + start;
      item = data[index];
      parsed[i] = {
        x: xScale.parse(resolveObjectKey(item, xAxisKey), index),
        y: yScale.parse(resolveObjectKey(item, yAxisKey), index)
      };
    }
    return parsed;
  }
Parse array of objects
@param {object} meta - dataset meta
@param {array} data - data array. Example [{x:1, y:5}, {x:2, y:10}]
@param {number} start - start index
@param {number} count - number of items to parse
@returns {object} parsed item - item containing index and a parsed value
for each scale id. _custom is optional
Example: {xScale0: 0, yScale0: 1, _custom: {r: 10, foo: 'bar'}}
@protected