whole_func_string: function getCategories(props, axis) {
    return props.categories && !Array.isArray(props.categories)
      ? props.categories[axis]
      : props.categories;
  }
func_code_string: function getCategories(props, axis) {
    return props.categories && !Array.isArray(props.categories)
      ? props.categories[axis]
      : props.categories;
  }
func_documentation_string: Returns an array of categories for a given axis
  @param {Object} props: the props object
  @param {String} axis: the current axis
  @returns {Array} an array of categories