code: def is_null(t):
      """
      Return True if value is an instance of type: {datatype}.
  
      Parameters
      ----------
      t : DataType
      """
      return t.id == lib.Type_NA
  
imports: from pyarrow.lib import is_boolean_value, is_integer_value, is_float_value
  import pyarrow.lib
  from pyarrow.util import doc
label_desc: Use image node_id 1 for calling a global function with example usage: is_null(t) and returns: unknown