code: def test_positive_domain(self):
      data = pd.Series([-1, -2, -100, 5, 10, 15])
      for encoder in [NumericEncoder(), TsNumericEncoder()]:
          encoder.is_target = True  # only affects target values
          encoder.positive_domain = True
          encoder.prepare(data)
          decoded_vals = encoder.decode(encoder.encode(data))
  
          for val in decoded_vals:
              self.assertTrue(val >= 0)
  
file_path: lightwood/tests/unit_tests/encoder/numeric/test_numeric.py
imports: import unittest
  import numpy
  import pandas
  import torch
  from lightwood.encoder.numeric import NumericEncoder
  from lightwood.encoder.numeric import TsNumericEncoder
  from lightwood.helpers.general import is_none
label_desc: Use image node_id 2 for calling the TestNumericEncoder obj's underlying member method code with example usage: obj.test_positive_domain() without return types