class_docstr: Encodes a scalar into a spark dataframe field.
code: def decode(self, unischema_field, value):
      # We are using pyarrow.serialize that does not support Decimal field types.
      # Tensorflow does not support Decimal types neither. We convert all decimals to
      # strings hence prevent Decimals from getting into anywhere in the reader. We may
      # choose to resurrect Decimals support in the future.
      return unischema_field.numpy_dtype(value)
  
imports: from abc import abstractmethod
  from io import BytesIO
  import numpy
label_desc: Use image node_id 3 for calling the ScalarCodec obj's underlying member method code with example usage: obj.decode(unischema_field, value) and returns: unischema_field