class_docstr: A simple in-memory FXRateReader.
  
  This is primarily used for testing.
  
  Parameters
  ----------
  data : dict
      Nested map from rate name -> quote currency -> pd.DataFrame
      Leaf frames should be indexed by (dates, base currencies).
  default_rate : str
      Rate to use when ``get_rates`` is called with a rate of 'default'.
code: def __init__(self, data, default_rate):
      self._data = data
      self._default_rate = default_rate
  
imports: from interface import implements
  import numpy
  from .base import FXRateReader, DEFAULT_FX_RATE
  from .utils import check_dts
label_desc: Use image node_id 1 to create a new InMemoryFXRateReader object from inherited base classes:  with example: obj = InMemoryFXRateReader(data, default_rate)