class_docstr: Determines the day of the month from a datetime.
  
  Examples:
      >>> from datetime import datetime
      >>> dates = [datetime(2019, 3, 1),
      ...          datetime(2019, 3, 3),
      ...          datetime(2019, 3, 31)]
      >>> day = Day()
      >>> day(dates).tolist()
      [1, 3, 31]
code: def get_function(self):
      def day(vals):
          return vals.dt.day
  
      return day
  
imports: from woodwork.column_schema import ColumnSchema
  from woodwork.logical_types import Datetime, Ordinal
  from featuretools.primitives.base import TransformPrimitive
  from featuretools.utils.gen_utils import Library
label_desc: Use image node_id 1 for calling the Day obj's underlying member method code with example usage: obj.get_function() and returns: day, vals