""" Provides basic funtionality for payload backends.
"""

# Local imports.
from IPython.zmq.ipkernel import Kernel


def add_plot_payload(format, data, metadata={}):
    """ Add a plot payload to the current execution reply.

    Parameters:
    -----------
    format : str
        Identifies the format of the plot data.

    data : str
        The raw plot data.

    metadata : dict, optional [default empty]
        Allows for specification of additional information about the plot data.
    """
    payload = dict(format=format, data=data, metadata=metadata)
    Kernel.get_kernel().add_exec_payload('plot', payload)