code: def _check_dynamic(dynamic, start, end, nobs):
      """
      Verify dynamic and warn or error if issues
  
      Parameters
      ----------
      dynamic : {int, None}
          The offset relative to start of the dynamic forecasts. None if no
          dynamic forecasts are required.
      start : int
          The location of the first forecast.
      end : int
          The location of the final forecast (inclusive).
      nobs : int
          The number of observations in the time series.
  
      Returns
      -------
      dynamic : {int, None}
          The start location of the first dynamic forecast. None if there
          are no in-sample dynamic forecasts.
      ndynamic : int
          The number of dynamic forecasts
      """
      if dynamic is None:
          return dynamic, 0
  
      # Replace the relative dynamic offset with an absolute offset
      dynamic = start + dynamic
  
      # Validate the `dynamic` parameter
      if dynamic < 0:
          raise ValueError(
              "Dynamic prediction cannot begin prior to the"
              " first observation in the sample."
          )
      elif dynamic > end:
          warn(
              "Dynamic prediction specified to begin after the end of"
              " prediction, and so has no effect.",
              ValueWarning,
          )
          return None, 0
      elif dynamic > nobs:
          warn(
              "Dynamic prediction specified to begin during"
              " out-of-sample forecasting period, and so has no"
              " effect.",
              ValueWarning,
          )
          return None, 0
  
      # Get the total size of the desired dynamic forecasting component
      # Note: the first `dynamic` periods of prediction are actually
      # *not* dynamic, because dynamic prediction begins at observation
      # `dynamic`.
      ndynamic = max(0, min(end, nobs) - dynamic)
      return dynamic, ndynamic
  
imports: import contextlib
  from warnings import warn
  import numpy
  from .representation import OptionWrapper, Representation, FrozenRepresentation
  from .tools import reorder_missing_matrix, reorder_missing_vector
  from .None import tools
  from statsmodels.tools.sm_exceptions import ValueWarning
label_desc: Use image node_id 1 for calling a global function with example usage: _check_dynamic(dynamic, start, end, nobs) and returns: dynamic,  ndynamic, dynamic,  int, None,  int, None,  int