class_docstr: Calculates the variance of a list of numbers.
  
  Description:
      Given a list of numbers, return the variance,
      using numpy's built-in variance function. Nan
      values in a series will be ignored. Return nan
      when the series is empty or entirely null.
  
  Examples:
      >>> variance = Variance()
      >>> variance([0, 3, 4, 3])
      2.25
  
      Null values in a series will be ignored.
  
      >>> variance = Variance()
      >>> variance([0, 3, 4, 3, None])
      2.25
code: def get_function(self):
      return np.var
  
imports: import numpy
  from woodwork.column_schema import ColumnSchema
  from woodwork.logical_types import Double
  from featuretools.primitives.base import AggregationPrimitive
label_desc: Use image node_id 1 for calling the Variance obj's underlying member method code with example usage: obj.get_function() and returns: np