How to use the simpleeval.DEFAULT_OPERATORS function in simpleeval

import six
from six.moves import range


def safe_pow_fn(a, b):
    raise InvalidExpression


def safe_range(start, *args):
    ret = list(range(start, *args))
    if len(ret) < 100:
        return ret
    return None


SAFE_OPERATORS = copy.copy(DEFAULT_OPERATORS)
SAFE_OPERATORS[ast.Pow] = safe_pow_fn  # don't allow power operations

FUNCTIONS = DEFAULT_FUNCTIONS
FUNCTIONS.update({
    'timedelta_to_seconds': lambda x: x.total_seconds() if isinstance(x, timedelta) else None,
    'range': safe_range
})


def eval_statements(statement, variable_context):
    """Evaluates math statements and returns the value

    args
        statement: a simple python-like math statement
        variable_context: a dict with variable names as key and assigned values as dict values
    """