Metadata API

mmodel provides a metadata API to fully customize the __str__ output of the node, graph, model, and modelgroup object outputs.

Here is an example to define a custom formatter for the node object:

from mmodel.metadata import MetaDataFormatter, wrapper80
from mmodel import Node

nodeformatter = MetaDataFormatter(
    formatter_dict={
        "name": format_value,
        "node_func": format_func,
        "output": lambda key, value: [f"return: {value}"],
        "doc": format_shortdocstring,
    },
    meta_order=["name", "_", "node_func", "output", "_", "doc"],
    text_wrapper=wrapper80,
    shorten_list=["doc"],
    shorten_placeholder="...",
)

The MetaDataFormatter class takes several parameters.

• formatter_dict: a dictionary specifies the formatter function for each metadata key.

• meta_order: a list specifies the order of the metadata keys. “_” is used to add a blank line.

• text_wrapper: a textwrapper class that is used to wrap the text to desired width for the whole

• shorten_list: a list of metadata keys that should be shortened if the text is too long. The shortening is done by the text_wrapper.

• shorten_placeholder: a string that is used to replace the shortened text.

The formatter function is defined to with “key” and “value” arguments, and returns a list of strings that will be format to lines. The “key” is the metadata key, and the value is the content of the metadata. If the key is in meta_order, but the formatter function is not defined, the value of the key will be used as the string representation.

An example of the formatter function is shown below:

def format_list(key, value):
    """Format the metadata value that is a list."""

    if not value:
        return []
    elements = [f"\t- {v}" for v in value]
    return [f"{key}:"] + elements

In this function format the list content with a tab and a hyphen. If the value is empty, then the metadata is not included in the output.

The formatter can be directly applied to a node object, or a custom node class can be defined:

class CustomNode(Node):
    def __str__(self):
        return nodeformatter(self)

mmodel.metadata.MetaDataFormatter(...)

Metadata Formatter.

See Metadata for the full list of metadata formatter functions.